Hillary Clinton and William Hague hail US-UK bond
The relationship between the UK and the United States is "unique and indispensable", Foreign Secretary William Hague has said.
In a joint press conference with US Secretary of State Hillary Clinton, Mr Hague said the two countries stood side by side on issues like the Middle East peace process.
Mrs Clinton said the US and UK had "a great working relationship".
US President Barack Obama has arrived in the UK ahead of a state visit.
In a joint article for the Times, Mr Obama and UK Prime Minister David Cameron said the UK-US bond was "not just special" but "essential" - to both countries and to the world at large.
"When the United States and Britain stand together, our people and people around the world can become more secure and more prosperous," they wrote.
"It is a perfect alignment of what we both need and what we both believe. And the reason it remains strong is because it delivers time and again."
Earlier, it was announced that the UK and US were setting up a joint body, the National Security Strategy Board, to look at threats from terrorism and rogue states.
The two politicians held talks on Monday afternoon on a range of foreign policy matters, including the recent political unrest in countries like Libya, Syria, Sudan and Yemen.
Mr Hague said the uprisings had brought "renewed hope of a better life" to millions of people, but warned that this period was also "marked by violence and uncertainty".
He said the US and UK would work closely together to support democracy and condemn repression.
There has been criticism in some quarters that the US is taking a back seat in the Nato-led effort to protect the Libyan population from attacks by Col Gaddafi's forces.
But Mrs Clinton said the US continued to fly 25% of all daily sorties over Libya, while Mr Hague said no-one should "underestimate in any way the huge contribution the United States has made".
Last week, following a meeting with Israeli Prime Minister Benjamin Netanyahu, President Obama said any future Palestinian state must be based on the borders that existed prior to the 1967 war.
Mr Hague has already welcomed that statement and he re-iterated that at the news conference, while stressing the urgent need for action.
"Time is running out for a two-state solution and the initiative must be seized now," he said.
Mrs Clinton added: "Now is the time, in this period of great upheaval, there is an opportunity to come to a successful outcome."
'Stop the killings'
Both ministers condemned the violence in Syria where human rights activists say more than 850 people have been killed since March by security forces trying to quell unrest.
On Monday, the European Union announced that it would join the US and impose sanctions on Syrian President Bashar al-Assad.
Mrs Clinton said: "Foreign Secretary Hague and I are absolutely consistent with our message to the Assad government.
"Stop the killings, the beatings the arrests, release all political prisoners and detainees. Begin to respond to the demands that are upon you for a process of credible and inclusive democratic change."
Her UK counterpart added: "Syria must change course."
President Obama had been due to fly into the UK on Tuesday, but his arrival has been moved forward to Monday night due to fears that ash from an Icelandic volcano could disrupt flights.
He and his wife will stay at Buckingham Palace as guests of the Queen, and the president will hold talks with Prime Minister David Cameron at 10 Downing Street.