ISRAEL threatened to step up its offensive in southern Lebanon yesterday as a UN plan to halt the fighting stalled in the face of Arab opposition.

Attempting to pressurise Lebanon into accepting the UN proposals, Israel said that it would intensify its military operation if there was not a diplomatic breakthrough within days. Throughout the day Israeli artillery pounded positions in southern Lebanon.

Last night two huge explosions ripped through the Shiyah area of southern Beirut. The Israeli airstrike caused 20 deaths and about the same number of casualties. Survivors said that the first blast demolished a six-storey block, while the second peeled away the sides of adjoining buildings.

Visiting frontline troops, Ehud Olmert, the Israeli Prime Minister, said that he would impose “no limits” on his army. “I give you all the means that you need, and all my support.”

But, after a meeting with the Lebanese Government in Beirut, the Arab League is sending a delegation to the UN today to press for changes to the plan, which would allow Israeli troops to remain in southern Lebanon until an international force takes over.

A vote on that plan, originally expected as early as yesterday, will now be delayed until later in the week. Last night France, one of the resolution’s sponsors, formally asked for a delay. “I am going to work today to improve the text,” Jean-Marc de la Sablière, the French envoy to the UN, said. “We have to take into account the concerns of all.”

Beirut’s main demand is that Israel withdraw its 10,000 troops from Lebanon and hand over a sliver of disputed territory known as the Shebaa Farms.

Fouad Siniora, the Lebanese Prime Minister, made a tearful appeal to the Arab foreign ministers, who flew into Beirut and drove past the smoking ruins of the southern suburbs, which have been pounded by Israeli airstrikes. He said: “I won’t allow Lebanon to be a punch bag for the Israelis.”

Diplomats were frustrated by the last-minute intervention, but still hoped that a compromise wording could be finalised in the coming days.

When that happens foreign ministers will assemble for a vote in the Security Council. Margaret Beckett, the Foreign Secretary, who is on holiday in France, is on standby to travel to New York when the wording of the resolution is agreed. While all sides want Israel to withdraw its forces from Lebanon, Israel and its allies are adamant that Hezbollah must not be allowed to re-establish its military dominance in the area.

Last night Lebanon mobilised 6,000 reserve soldiers and agreed to send 15,000 troops to the south to police any ceasefire once Israel withdraws. In the past the Lebanese Army has failed to disarm or even challenge Hezbollah’s forces.

“Whatever happens in the UN, we must not create a vacuum into which Hezbollah and its sponsors are able to move more weapons,” President Bush said.

The situation on the ground continued to deteriorate with Israeli warplanes bombing suspected Hezbollah targets as well as the remains of Lebanon’s shattered infrastructure. Three Israeli soldiers were killed by Hezbollah guerrillas.

Israel ordered its forces to step up operations against Hezbollah in southern Lebanon and imposed a curfew in southern Lebanon to bann traffic from 7pm.

Despite a month of sustained attack Hezbollah is still operating effectively in southern Lebanon. Yesterday it attempted to fly a drone into Israel, which was shot down over the border.

On the spot reports from the Middle East

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