US Secretary of State Condoleezza Rice has pledged Washington's support for beleaguered Palestinian Authority President Mahmoud Abbas.
Ms Rice said the US admired Mr Abbas' leadership
Speaking after meeting Mr Abbas in the West Bank town of Ramallah, Ms Rice said the US had "great admiration" for his leadership.
Her comments came after Mr Abbas said talks with Hamas on forming a national unity government had collapsed.
Ms Rice later dined with Israeli Prime Minister Ehud Olmert in Jerusalem.
According to Israeli officials quoted by the Reuters news agency, Mr Olmert told Ms Rice Israel plans to open its main commercial border post with Gaza shortly.
The crossing at Karni is frequently sealed over Israeli security fears.
Mr Olmert's office also released a statement saying it would not release Palestinian prisoners until an Israeli soldier captured by Hamas-linked militants is set free.
Cpl Gilad Shalit was seized in a cross-border raid in June, setting off a series of Israeli military operations in Gaza.
Ms Rice is expected to meet Israel's Foreign Minister, Tzipi Livni, and the Defence Minister, Amir Peretz, on Thursday.
Her visit is part of a wider Middle East trip aimed at reinforcing support for moderate leaders.
But the BBC's state department correspondent Jonathan Beale says while Ms Rice poured praise on the Palestinian leader, she appeared to have little to offer him.
She said the US wanted to do more and was discussing how to facilitate a meeting between Mr Olmert and Mr Abbas.
But, our correspondent says, there was no indication that the US had a plan to restart the peace process.
Ms Rice had no contact with Hamas officials during her trip.
Hamas leader Ismail Haniya accused the US diplomat of seeking to "rearrange" the region to suit US and Israeli interests.
At a joint news conference in Ramallah, Ms Rice reiterated Washington's support for a two-state solution to the Israeli-Palestinian conflict.
"You have the strong commitment of the United States to that cause and the personal commitment of me and the personal commitment of the president," she told Mr Abbas.
She said the US was very concerned about the deteriorating humanitarian situation in the West Bank and Gaza, and promised to "redouble our efforts to improve the conditions for the Palestinian people".
The BBC's diplomatic correspondent Jonathan Marcus says Ms Rice's focus on this trip has been both to bolster Mr Abbas but also to try to secure some safety valve for the tensions building up in the Palestinian territories - not least by getting the Israelis to open some of the border crossings that are essential to the Palestinians' economic well-being.
But, he says, the Israelis have a price - better security and the return of their abducted soldier, Cpl Shalit.
Mr Abbas meanwhile said talks with Hamas to form a national unity government had collapsed.
"There is no dialogue now," he said. "I have also said that dialogue cannot continue forever.
"Therefore, we have to think long and hard about what we are going to do and what is the next step going to be."
The Palestinian Authority has faced a political crisis since Hamas won elections in January. Its refusal to recognise Israel and renounce violence triggered a Western boycott.
Over the past month, Mr Abbas has been seeking to form a coalition government with his more moderate Fatah party on a platform which would be acceptable to the international community.
The Hamas Prime Minister, Ismail Haniya, criticised Ms Rice's visit, saying the secretary of state "cares only to rearrange this region and to rearrange the Palestinian scene in a way that serves the American and Israeli agenda".
A flare-up of fighting between Hamas and Fatah gunmen in the West Bank and Gaza over the past few days claimed an 11th life on Wednesday.
Unidentified masked gunmen killed a Hamas leader in the West Bank city of Qalqilya, a day after Fatah-linked al-Aqsa Martyrs Brigades militants threatened to kill senior Hamas members.