The US and Israel will not work with a new Palestinian unity government unless it recognises Israel, Prime Minister Ehud Olmert has said.
Ms Rice is to hold joint talks with Mr Abbas and Mr Olmert on Monday
He was speaking a day before three-way talks with US Secretary of State Condoleezza Rice and Palestinian Authority President Mahmoud Abbas.
Ms Rice held separate talks with both men on Sunday.
Publicly, she said the US would "await the formation of a [unity] government before making any decisions".
Hamas, the largest group in the proposed Palestinian unity government, refuses to recognise Israel.
Mr Olmert said a Palestinian government that failed to accept conditions laid down by the quartet of the US, EU, Russia and UN "cannot receive recognition and there will not be co-operation with it".
"I spoke about this on Friday with the president of the United States, and I can tell you the Israeli and US positions are completely identical," Mr Olmert said in televised comments.
The EU, US and Russia have maintained an economic boycott of the Palestinian government since Hamas won legislative elections in January last year.
After weeks of internal fighting, Hamas and the rival Fatah faction agreed last week to form a national unity government.
As a result, Ismail Haniya, of Hamas, resigned from his post as prime minister on Thursday and was asked by Mr Abbas, who heads Fatah, to form a new national unity government.
Ms Rice spent more than two hours in talks with Mr Abbas in the West Bank town of Ramallah. She then held talks in Jerusalem with Mr Olmert.
Before those meetings, Ms Rice said it was an important time to advance the vision of a Palestinian state.
Mr Olmert's comments will add to doubts about whether the US will engage with a new Palestinian unity government.
Many observers wonder whether the two embattled leaders, Mr Olmert and Mr Abbas, are strong enough to take the difficult steps towards peace, says the BBC's Bethany Bell in Jerusalem.
Speaking after talks with Israel's Foreign Minister Tzipi Livni, Ms Rice said now was "an important time to talk about how we advance the vision of two states living side-by-side in peace and in freedom".
But she and Ms Livni both stressed that any new Palestinian coalition government must recognise Israel, renounce violence and accept past peace agreements.
Mr Abbas (right) charged Mr Haniya with forming a unity government
Hamas' refusal to recognise Israel has led to a crippling ban on Western financial aid since the party came to power.
Meanwhile, factional fighting between Fatah and Hamas has claimed more than 90 Palestinian lives since December.
Mr Haniya now has five weeks to get a new cabinet accepted by the Hamas-dominated parliament.
But if Hamas maintains its position regarding Israel, there is concern that any talks brokered by Washington will be futile, correspondents say.