Tony Blair today acknowledged that there was a risk that the destruction and death in the Middle East could fuel extremism.

The Prime Minister said that in the short term the outrage at civilian deaths in Lebanon could make finding a solution to the conflict between Israel and Hezbollah harder.

"It's a perfectly valid point that there may be so much damage done in the short term that it becomes more difficult to find a long term solution in the future," said Mr Blair.

"No sentient human being could fail to be moved by the suffering and death. It's terrible."

But, he added, this only fuelled his determination to find a lasting solution to the conflict that could pave the way for a long term peace.

Mr Blair was seeking to face down the voices of criticism that have grown louder while he has been away on a six day visit to the United States. His stance on Lebanon and Israel - blocking calls for an immediate ceasefire and refusing to criticise Israel's military campaign in southern Lebanon that has left more than 700 people dead on the Lebanese side, as well as more than 50 in Israel - has caused enormous unease in the Cabinet, the Parliamentary Labour Party and the country at large.

Jack Straw, the leader of the Commons, became the most senior Labour figure openly to voice dissent, when last weekend he called Israel's bombing of Lebanon "disproportionate" - a legally loaded term that hints at war crimes.

Today Mr Blair said that he was not surprised that people in the Cabinet had doubts. But he drew a distinction between voicing distress at the deaths and wanting them to stop at once - a view which he said everyone shared - and the process of finding a working solution.

"It doesn't surprise me at all that people are concerned or worried. I don't disrespect what they say, or fail to understand why they say it. But I am trying to get a practical solution."

He appeared to aim a sideswipe at armchair critics of his stance who had no alternative long term policy. Any ceasefire would have to be agreed by both sides - and that meant it must be agreed by the Hezbollah ministers in the government of Fouad SIniora, the Prime Minister of Lebanon, as well as the more moderate voices, he said.

"There's no point saying there has got to be a ceasefire, but only on one side," he told a Downing Street press conference

"Unless we get an agreement that involves not just Prime Minister Siniora but the whole government of Lebanon, and put it in place in such a way that it's going to hold, we are just expressing a view, we are not getting the job done.

"The reason for the problem is that, in defiance of UN Resolution 1559 (which called for Syrian withdrawal from Lebanon and the disarming of sectarian militias), Hezbollah has continued to operate with their militia in the south of Lebanon. The conflict started when Hezbollah crossed the UN blue line.

"We grieve for the innocent Israelis who have died, we grieve for the innocent Lebanese who have died. A solution will not come by sympathising with one side, or by the statements we make, it will only come by dealing with both sides."

He strongly played down accusations that the rifts in his Cabinet were serious, categorically denying reports that he has had differences with Margaret Beckett, the Foreign Secretary, or that senior Foreign Office officials had been pleading with him to take a different tack.

Mr Blair returned to elements of a foreign policy speech he gave in the US last week, stating that the Middle East and the world faced a stark choice between extremism and moderation. The West must work with moderate Muslim opinion for long term peace, stability and democracy, or hand over the fate of the Middle East to the religious extremists, he warned.

This meant a redefinition of President Bush's war on terror to work with Muslim moderates, Mr Blair said. He warned that the disquiet felt in moderate Islamic countries that nothing is being done to solve the Israeli-Palestinian conflict was very serious issue, and said that it was important to get back to underlying issue of MIddle East peace process as soon as Lebanon has quietened down.

Mr Blair condemned as shocking and very unhelpful the comments made today by Mahmoud Ahmadinejad, the Iranian President, that the solution to the Middle East crisis lay in the elimination of Israel.

Syria and Iran should try to help to solve problem, he said.

He denied that anyone was proposing military action against either state, but strongly attacked Iran for arming and financing Hezbollah - with virtually identical weaponry to the bombs being used against British soldiers in Basra, he added pointedly - and for trying to seek an atomic bomb in defiance of international law.

Mr Blair also said he was disappointed at the court ruling that control orders - intended to allow for the monitoring of terror suspects - breached human rights.

He added that plans for identity cards would go ahead in Britain, to combat terrorism. MPs are due to publish a report tomorrow on the spiralling costs of the identity cards scheme.

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