The rising concern that any further Israeli military action could intensify the crisis, expressed by senior officials yesterday, strikes a much more urgent tone than the American position, which accepts a continued Israeli campaign to crush the Shia militant group.

Yesterday was the heaviest day for civilian casualties since Israel’s bombardment began last week, with at least 63 killed and scores more wounded. A total of 315 Lebanese, mostly civilians, have been killed and hundreds injured since the start of the Israeli offensive.

Last night dozens of planes dropped 23 tonnes of explosives on what the Army said was a bunker in south Beirut used by Hezbollah’s leadership. The group said none of is leaders where killed in the attack.

A senior British official said: “Our concern is that Israeli military action is not having the desired effect. We’re not seeing the level of impact [which Israel and its allies would want].” Hezbollah was “still highprofile in southern Beirut”, even if its claims to have lost only three fighters underplayed the damage done. “We’re not seeing any large-scale destruction of Hezbollah rockets,” the official added, “and we don’t know where they are.”

Israel claimed yesterday to have destroyed half of Hezbollah’s rockets, which the guerrilla group has been firing steadily across the Lebanese border. “We have already destroyed around 50 per cent of the rockets and missiles that Hezbollah had,” General Alon Friedman told army radio.

The Israeli action had “disrupted Hezbollah but there’s not much more they can do with an extensive campaign”, a British official said. “We are concerned that continued military operations by Israel will cause further damage to infrastructure and loss of civilian life which the damage to Hezbollah will not justify.”

But the need for Ehud Olmert, the Israeli Prime Minister, to appear tough at home might tempt him to continue even when the military value was slight, officials suggested.

The Bush Administration, by contrast, has given Israel a green light to continue its attempt to crush Hezbollah.

Condoleezza Rice, the Secretary of State, is now expected to visit the region on Sunday in a sign of greater US engagement, that will be welcomed by European governments. Today, at the UN Security Council in New York, Britain will push for a set of “guidelines for the next phase” which go further than the G8 summit managed last week. “We do need a plan, partly to give Israel a reason to stop its military action,” the official said. Britain and the US also want to show Iran, Hezbollah’s backers, that it cannot ignite such conflicts.

But the meeting will expose differences within the council — and between Britain and the US. There are deep disagreements about how to respond to the crisis, which began nine days ago with Hezbollah’s kidnapping of Israeli soldiers.

The heart of the British plan is the proposal, promoted by Tony Blair at the G8 summit, for an international force in southern Lebanon to allow Lebanese security forces to regain control from Hezbollah. The US has been sceptical of the idea. Britain has also been anxious about the lack of urgency shown by the US, reflected in the nine days that it has taken to assemble the Council.

On Tuesday, Dr Rice said that there should be a ceasefire “as soon as possible when conditions are conducive to do so”, words widely interpreted as licence for Israel to continue.

France, which backs the notion of an international force, also wants the Council to call for a ceasefire, a demand on Israel which the US and Britain are unlikely to accept.

The first sign of British frustration at the US position came during the summit when, in an unguarded conversation with Mr Bush, Mr Blair revealed his anxiety about the need for urgent intervention. The Prime Minister suggested that he could visit the region immediately if a trip by Dr Rice took too long to arrange.

However, in the Commons yesterday, Mr Blair backed Israel’s right to defend itself, provided that it “does its best to minimise civilian casualties”, a position matching that of the US. This conflict “started with the kidnap of Israeli soldiers and the bombardment of northern Israel”, he told Sir Menzies Campbell when challenged to say whether it was US policy to tolerate further Israeli military action. Mr Blair mocked Sir Menzies for saying that Britain should call for an “immediate and unconditional ceasefire”. Hezbollah had sent “ in the region of 1,600 rockets into northern Israel”, and while that continued, a “proportionate” response was justified.

THE TOLL

• In the nine days since fighting in Lebanon began

  315 Lebanese killed

  31 Israelis killed

• In the 25 days since first Israeli soldier kidnapped in Gaza

  93 Palestinians killed

  1 Israeli killed

• 500,000 the number of displaced people in Lebanon, Unicef says

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president