The aftermath of Saudi coalition airstrike in Saada in August (Picture: PA).
A ceasefire in Yemen will only have an effect if it is "underpinned by a political deal", Theresa May said after the US administration called for a halt to the conflict.
The Prime Minister backed the US call for "de-escalation" but added that a lasting political settlement was necessary.
Shadow foreign secretary Emily Thornberry claimed the UK had played a "shameful" role in the conflict by supporting arms sales to Saudi Arabia, the leading nation in the coalition fighting Houthi rebels.
She also claimed a draft resolution drawn up by the UK at the United Nations was shelved two years ago in response to Saudi assurances.
At Prime Minister's Questions, Mrs May was urged by former cabinet minister Andrew Mitchell to press for a new UN Security Council resolution demanding an immediate ceasefire.
Theresa May said "we back the US's call for de-escalation in Yemen" and in March the UK had "proposed and co-ordinated a UN Security Council presidential statement which called on the parties to agree steps towards a ceasefire".
She said that remained the UK's position but "a nationwide ceasefire will only have an effect on the ground if it is underpinned by a political deal between the conflict parties".
Ms Thornberry said she was "heartened" by the US stance but added the UK had a "culpability" over the war.
US secretary of state Mike Pompeo called for an urgent halt to the war and the start of negotiations towards a political settlement.
US defence secretary Jim Mattis has called for a ceasefire within 30 days.
The Trump administration's renewed call for a political solution follows Western criticism of Saudi Arabia over the killing of journalist Jamal Khashoggi in the kingdom's consulate in Istanbul.