Jack Straw has defended the government's support for Israeli plans to withdraw from the Gaza Strip and parts of the West Bank.

The move was put forward by Israeli premier Arial Sharon, who also secured President Bush's backing on the key issues of rights of return for refugees and recognition of some major settlements in the West Bank.

However, members of Sharon's ruling Likud party rejected the plan, leaving its current status uncertain.

Speaking in the Commons on Tuesday, the foreign secretary said the planned pullout was "in line" with the road map.

"It is the road map...which is fundamental to a peaceful settlement in the Middle East," he added.

Straw said the UK was "fully engaged in making what progress we can", despite the "setback" of the Likud referendum.

He added that any withdrawal by Israel should not prejudge the final status talks.

The foreign secretary also said the Palestinian Authority should do more to improve security and prevent terrorist attacks, while Israel should withdraw from those territories required in the road map.

Labour MP Jim Cunningham warned that hopes of a Palestinian state were "slipping".

But despite the controversial concessions by President Bush, Straw insisted the US was "fully committed" to the road map.

And responding to a warning from Plaid Cymru's Elfyn Llwyd that Israel was "choking" the Palestinian economy, the foreign secretary said he would continue to press Israel to lift restrictions which make life "much more difficult within the occupied territories".

"At the same time it has to be put on record that the sooner that the PA gets a real and convincing grip of rejectionist territory groups operating within those territories, the easier life will be and the easier too it will be for the Israeli government to lift some of those restrictions," he added.

"The roadmap lays down obligations on each party...what is crucial is that each party, Israel and the Palestinian Authority, instead of complaining about the other, take the steps which they are obliged to take to implement the roadmap."

Conservative spokesman Gary Streeter called on the government to ensure that the roadmap remains "on track".

Straw accepted that "delay is more likely than rapid progress" but pledged the UK would do "all we can" to implement the roadmap.

Any withdrawal was always likely to be on a phased basis, he added.

"We should not get into a position where, because we cannot have everything all at once, we should take nothing," he said.

"That was why this policy of withdrawal was welcomed.  I hope very much the Israeli government will be able to resurrect it."