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The world's major powers are assessing the implications of this week's announcement that the US intends to press ahead with a controversial missile defense system.
President George W Bush said that to develop the missile shield -dubbed "Son of Star Wars"- his country would abandon the 1972 Anti Ballistic Missile (ABM) Treaty, seen by many as a cornerstone of world arms control agreements.
But the US President said the ABM treaty was a relic of the Cold War and a new defence framework was needed to protect America and its allies from modern-day threats.
But there are still serious doubts about the viability of such a system, its cost and the impact it will have on the international nuclear power balance.
Will it work? Will it make the world safer, or could it lead to a new arms race?
Caspar Weinberger was Ronald Reagan's secretary of Defense from 1980 to 1987. He was also an advisor to President George Bush until 1990.
Highlights of interview:
Robert Barker, London, UK:
As an American living overseas I am appalled at the current course of action proposed by Mr Bush. Why does Mr Bush want to throw away the ABM treaty and take us back to the days of the Cold War?
The treaty was in 1972 - the Cold War was considerably before that. The theory is that the people supporting the ABM treaty seems to me to be that it will prevent an arms race which I think is perfect nonsense because we have had an arms race all the time we have had the ABM treaty and we have seen the greatest increase in proliferation of nuclear weapons that we have ever had. We are up to 7,000 plus, the Russians are up to 6,900 plus. On intercontinental missiles the Russians have 23,000 nuclear warheads. So the ABM treaty preventing an arms race is total nonsense.
Judah Feingold, Plattsburgh, USA:
Why would the U.S. not pursue the same goal by using its intelligence and networking with the rest of the world to ensure that rogue states cannot be armed with nuclear weapons?
That would be very nice if it could happen but I don't how any networking is going to prevent North Korea from doing everything it can to get more nuclear weapons than they have now particularly when China and Russia are perfectly willing to sell them all of the technology required. Intelligence sources aren't going to prevent a country from doing it.
You have to understand that without any defences whatever you are very vulnerable. It is like of both sides would say we don't like chemical warfare - we don't like gas attacks - so we are going to give up and promise not to have any defences ever against them and that of course would mean then we are perfectly safe. As a former commander of troops, I would not want to send our troops out in the battlefield situation where we had no defences whatsoever against chemical weapons.
Richard, Cheshire, UK:
In the light of the failure of the Patriot missile interceptor system in the Gulf war and the failure of all but one of the recent system tests will this system work?
The Patriot was not a failure in the Gulf War - the Patriot was one of the things which defeated the Scud and in effect helped us win the Gulf War. One of two of the shots went astray but that is true of every weapon system that has ever been invented.
Stephen R Darlington, Leeds, England:
Surely the real danger to American soil and the American people is from suitcase bombs and Tokyo-subway style terrorist attacks which the missile shield would do nothing to prevent?
Well that is correct but because one form of disaster is possible to happen doesn't mean that you shouldn't take precautions against every other one.
The fact that a missile defence system wouldn't necessarily block a suitcase bomb is certainly not an argument for not proceeding with a missile defence when a missile that hits can wipe out hundreds of thousands of lives in a second.
Daniel Spence, Nashville, USA:
It's not as if we are creating a great, new offensive weapon. Why is the pursuit of a defensive measure so threatening to other countries?
The curious thing about it is that missile defence is not an offensive weapon system - missile defence cannot kill anybody. Missile defence can help preserve and protect your people and our allies and the idea that you are somehow endangering people by having a defence strikes me almost as absurd as saying you endanger people by having a gas mask in a gas attack.
Greg Knight, Rochester MN, USA:
I once heard you say that the Russians have broken every arms treaty with the US that they ever signed. Is this still true, and if so, what does it matter if the ABM treaty is scrapped?
We have taken the ABM treaty as binding ourselves - the Soviets and now the Russians have not. They started on the working on a defensive system within a few weeks after signing the ABM treaty in 1972. It is their inability to get the system that has caused them so much anguish.
My worry is when we have Russia and China being the most vociferous opponents of the plan to abandon the ABM treaty and go to a defensive system. Why are they so vociferous about their hatred of the idea of having a defensive system? The answer, I am afraid is rather clear - it is because they have offensive plans that they think would be thwarted by a defensive system and so they are doing everything they can to try to block it.
Daniel Swartz, Munich, Germany:
Do you think it is wise to promote a missile defence plan at a time when tensions are on the rise not only with China, but also with Russia?
May I suggest that tensions on the rise because we don't have a defensive system. Tensions are on the rise because very aggressive powers know that the one system that will never be defended against if we follow the ABM treaty - the most lethal system in the world are these nuclear and chemical warhead carrying missiles. Now if you tell an aggressive nation that is the one system weapons that is never going to be defending against - what are they going to do? They are going to make every effort to get that kind of system of weapons. That is what is happening and that is why there is an increased tension. The greatest force for proliferation is the ABM treaty.
So that is why it seems to me that it is vital that we get rid of the ABM treaty concept as soon as possible and proceed with the construction of an effective defence to protect ourselves and our allies.
Alan Cheung, Oxford, London:
How does the US government rationalise the possibility of an arms race when promoting the missile shield? Are they thinking that an arms race is unlikely?
A point echoed by many others.
Another questioner asks:
In the long term, an effective defence shield may increase global stability.
But in the short-term would you agree that the world will be a more unstable and volatile place?
I think they are overlooking what is actually happening. President Bush said that we were going ahead with the defensive system but we would make sure that nobody felt we had offensive intentions because we would accompany it by a unilateral reduction of our nuclear arsenal. It seems to me to be a rather clear statement that proceeding with the missile defence system would mean fewer arms of this kind.
You have had your arms race all the time ABM treaty was in effect and now you have an enormous accumulation and increase of nuclear weapons and that was your arms race promoted by the ABM treaty. Now if you abolish the ABM treaty you are not going to get another arms race - you have got the arms already there - and if you accompany the missile defence construction with the unilateral reduction of our own nuclear arsenal then it seems to me you are finally getting some kind of inducement to reduce these weapons.
Matt Simon, USA:
Aren't the Star Wars and missile defence programs simply rather dangerous ways of granting lucrative contracts to the big-business allies of the Republican Party?
No. The answer is very simple and very clear. We have a military programme designed to reinvigorate and strengthen the military after eight long years of neglect under Mr Clinton.
You put out military contracts to the lowest bidder for the things you need. A great many of the arms companies and the military contractors in the United States are heavy contributors to the Democratic Party. The two are not connected. If you need military weapons you go to somebody who can build them. We do feel that we do need some kind of military capability in this rather unfriendly world.
So how do you react when many Europeans say that when Americans talk of extending this missile umbrella over Europe it is really a cynical mechanism for forcing us to buy American defence equipment?
These are people who don't understand how it works. Nobody is going to force anybody to buy anything. The kind of system that we are talking about which will require some co-operation in deployment is not a system which requires European or other nations under its umbrella to buy anything.