The United States and France were close to a deal on Friday on a UN resolution seeking an end to the fighting between Israel and Lebanon as the first step towards a political settlement of the conflict.
But France's UN ambassador, Jean-Marc de la Sabliere, told reporters after a second round of talks, "We're still working on it."
Once they reach agreement, which could occur over the weekend, a UN Security Council vote could be held within 24 hours, possibly with foreign ministers.
But with fighting raging, an end to hostilities still appears questionable, despite regular contacts by Washington and Paris with Israel and Lebanon.
US Ambassador John Bolton told reporters after talks with Mr Sabliere, "There are still some issues we've not resolved, but I think we've come a little bit closer."
In Washington, US State Department spokesman Sean McCormack said: "I think we are very close on coming up with a final draft text that could be shared among other council members. We are prepared to work through the weekend."
In a flurry of telephone diplomacy, UN Secretary-General Kofi Annan discussed the resolution with US President George W. Bush, French President Jacques Chirac, Prime Minister Tony Blair, Russian Deputy Foreign Minister Andrei Denisov and Lebanese Prime Minister Fouad Siniora, a UN spokesman said.
The Bush administration has been slammed by critics who accuse it of siding with ally Israel by not calling for an immediate end to the fighting, which has killed 720 Lebanese and 73 Israelis