An international force must be quickly despatched to Lebanon, US President George W Bush has said.
The leaders have been accused of condoning the Israeli offensive
After talks in Washington with UK Prime Minister Tony Blair, Mr Bush said the two countries' goal was to achieve a "lasting peace" in the region.
But neither called for an immediate ceasefire. The US secretary of state is returning to the region on Saturday.
Earlier, Hezbollah said it had fired a new long-range rocket, called the Khaibar-1, into northern Israel.
Meanwhile, the UN has called for a 72-hour truce in the conflict zone in southern Lebanon to allow humanitarian aid in and to get casualties out.
Mr Bush said he and Mr Blair had agreed an international force would augment the Lebanese army, and assist with the distribution of humanitarian aid.
He told reporters their top priorities in dealing with the crisis were to:
- Help provide immediate humanitarian relief
- Achieve an end to the violence
- Return those displaced by the crisis
- Help with reconstruction
Mr Bush said Condoleezza Rice would hold talks with the leaders of Israel and Lebanon to agree a proposal to achieve lasting peace.
The UN Security Council would meet next week to discuss the issue, he added.
"Our goal is a Chapter Seven resolution setting out a clear framework for cessation of hostilities on an urgent basis and mandating the multinational force," he said.
"Prime Minister Blair and I believe that this approach gives the best hope to end the violence and create lasting peace and stability in Lebanon."
The leaders' meeting comes amid growing pressure on the US and UK to join calls for an immediate ceasefire between Israel and Hezbollah.
But the BBC's James Coomerasamy in Washington said that their fundamental position did not appear to have changed - rather than demanding an immediate ceasefire, Mr Bush and Mr Blair called for a framework to enable the cessation of hostilities.
"This is a moment of intense conflict in the Middle East," Mr Bush said. "Yet our aim is to turn it into a moment of opportunity and a chance for broader change in the region."
Mr Blair said he and Mr Bush agreed that a UN resolution was needed as quickly as possible to stop the fighting in Lebanon.
But he warned: "Nothing will work unless as well as an end to the immediate crisis, we put in place the measures necessary to prevent it occurring again."
As the two leaders held talks, the violence continued on the ground.
Hezbollah said its new rocket had landed south of the city of Haifa, the deepest strike inside Israel so far.
Israeli police have confirmed that a previously unknown rocket carrying up to 100kg of explosives had struck an area near the town of Afula.
The attack came as the Israeli army said it would deploy patriot anti-missile batteries near Tel Aviv, Israel's largest city, in case Hezbollah started using longer-range missiles.
The strike formed part of a barrage of more 100 rockets fired into northern Israel, injuring at least seven people.
Israel has carried out dozens of fresh strikes on Lebanon. Lebanese officials said at least 12 people had been killed.
Israel said late on Friday that 26 Hezbollah fighters had been killed in fighting around the town of Bint Jbeil.
Earlier on Friday, two mortar rounds hit a convoy of vehicles carrying civilians escaping the violence in southern Lebanon. Two people travelling in a German TV car were wounded.
The convoy, organised by the Australian embassy, was returning to the port city of Tyre from the border village of Rmeish, where hundreds of people have been trapped by the Israeli offensive.
Our correspondent says the cars were clearly marked as a press and civilian convoy, and that individual journalists had been in contact with the Israelis who knew about the journey.
The Israeli Defence Forces said they did not believe the mortars were theirs but were still checking.
Some 425 Lebanese, the vast majority civilians, are confirmed killed in the 17 days of the conflict - but a Lebanese minister has suggested scores more bodies lie under the rubble.
Fifty-one Israelis, including at least 18 civilians, have been killed.
The Israeli assault began after Hezbollah captured two Israeli soldiers and killed eight in a cross-border raid on 12 July.
Israeli Defence Minister Amir Peretz stressed on Friday Israel had no plans to start operations against Syria.
In other developments:
- A Jordanian man was killed and at least three other people wounded in one of several strikes in Kfar Joz, close to the south Lebanese market town of Natabiyeh
- There were multiple strikes on the Bekaa Valley to the east, on villages around Tyre, and roads in the south-east
- Israeli soldiers killed at least 15 Hezbollah fighters in Bint Jbeil, the Israeli army said. Israel suffered its worst single losses in the southern town on Wednesday
- Unarmed UN observers have been temporarily relocated from border positions in southern Lebanon after the deaths of four UN observers in an Israeli strike on Tuesday
- Israeli military chief Dan Halutz was taken to hospital after feeling unwell but later returned home, Israeli Channel 10 TV reported.