William Hague says Syria's Assad 'must reform or go'
Foreign Secretary William Hague has said Syrian President Bashar al-Assad must implement reforms in his country or "step aside".
Arriving at an EU meeting in Luxembourg, Mr Hague said he also hoped Turkey would "bring every possible pressure to bear" on its neighbour.
The United Nations say at least 1,100 civilians have been killed since anti-government protests began in March.
UK nationals in Syria are being urged to leave immediately.
On Saturday, the UK Foreign Office strengthened its advice to the thousand or so British nationals registered with the embassy in the capital Damascus.
It is now urging them to leave urgently - regardless of whether they feel they have a pressing need to stay.
More than 10,000 Syrian refugees have fled over the border to Turkey in recent weeks to escape a violent crackdown on protesters by President Assad's forces.
Mr Hague said the Turkish government had an important role to play in trying to resolve the crisis.
"I know that Turkey has many contacts, much influence in Syria, so I hope our Turkish colleagues will bring every possible pressure to bear on the Assad regime with a very clear message that they are losing legitimacy [and] that Assad should reform or step aside.
"I hope they will be very clear and very bold about that."
At their meeting on Monday, Mr Hague and his fellow EU foreign ministers are expected to discuss the need to expand sanctions on Syria.
The summit is taking place as President Assad is due to make a televised address to the Syrian people.
It will be his first speech for two months, and only the third time he has spoken publicly since protests demanding greater freedoms and democracy erupted.
"The United Kingdom looks to him... to respond to legitimate grievances, to release prisoners of conscience, to open up access to the internet and freedom of the media, and to cooperate with the UN High Commissioner on Human Rights," Mr Hague said.
Britain, France, Germany and Portugal are pushing for a UN Security Council resolution condemning the military crackdown, but Russia has indicated that it will block the move.