Tony Blair was pressing on "hell for leather" last night with attempts to secure a United Nations resolution for a ceasefire in the Middle East.

The Prime Minister, on a visit to the US, had already spoken by telephone to the prime ministers of Israel and the Lebanon to try to help find an acceptable way forward, said his spokesman.

Mr Blair was also speaking to his counterparts in Turkey, Italy and Germany.

And the UK was involved in negotiations with the French and Americans at the UN, in New York, to draw up a resolution as soon as possible that could have an immediate impact on the ground.

"We are pushing with the same urgency - in fact I would say a greater urgency - for a resolution after the events of the last few days, as we were last week," the spokesman said.

"We believe a resolution can help bring this conflict to an end and I think the sooner we have it, the better. That's why we are still going hell for leather for a resolution.

"We are working flat out in London, in the UN and from here to try to reach the situation as quickly as possible where there is agreement on a text in New York.

"We hope that will then have an immediate effect on the ground."

His words came as Israeli PM Ehud Olmert said there would be no let-up in the offensive in the immediate future as air strikes continued.

A 48-hour halt to hostilities aimed at allowing civilians to leave and aid to get in did not hold after Hezbollah continued to fire rockets at Israeli targets.

It was called under US pressure following outrage over a strike on Sunday morning that levelled a house in Qana, killing at least 56 people - most of them women and children - who were taking refuge there.

Asked if the Prime Minister was disappointed that the halt had not been observed, the spokesman said: "There has been, as I understand it, action on both sides. The important point is that we negotiate to bring the action on all sides to a close. That's where our focus is."

Israeli Defence Minister Amir Peretz has said Israel plans to "expand and strengthen" its attack on Hezbollah.

Liberal Democrat defence spokesman Michael Moore said that was a major setback for diplomatic efforts.

And he called on Mr Blair and US President George Bush to put pressure on Israel to call an immediate ceasefire.

But the Prime Minister's spokes-man said "exhortation" would not resolve the situation.

"There are two sovereign governments here. This will not proceed unless those two sovereign governments are in broad agreement with where we're going," he said.

ä Life in Gaza - Page 10