US Secretary of State Condoleezza Rice has gone to the Middle-East to push for Israeli-Palestinian co-operation over Israel's planned Gaza pullout.
Ms Rice said the peace process was at a "critical" juncture
She is due to meet Israeli Prime Minister Ariel Sharon on Friday, before holding talks with Palestinian leader Mahmoud Abbas on Saturday.
Ms Rice's hastily arranged three-day visit follows an upsurge in violence.
It comes as Israel has said the August pullout may be brought forward to avoid further protests by Jewish settlers.
The visit is unlikely to offer anything new, says the BBC's Jonathan Beale, who is travelling with Ms Rice.
But it does show America's commitment to ensure Israel's withdrawal goes ahead as planned, our correspondent says.
'Moment of hope'
"This is a critical time in the history of this region because Prime Minister (Ariel) Sharon has taken an historic decision to disengage from the Gaza and four settlements in the West Bank," Ms Rice said after arriving in Jerusalem late on Thursday.
Some 20,000 police and soldiers have been deployed around Gaza
"I look forward to talking with both the Israelis and the Palestinians about the need for tight co-ordination," she said.
"I also look forward to talking about the need to resist any efforts by terrorists to destroy this moment of hope."
Ms Rice has praised Mr Abbas for taking a stand against those on his own side who have resumed attacks.
She still thinks the Palestinian Authority should do more to stem the violence, but she has also appealed to neighbouring Arab countries to help in those efforts, our correspondent says.
Mr Rice is also expected to urge restraint by Israel, following several days of protests by Jewish settlers.
A protest march to Gaza was called off on Thursday, but not before 20,000 police and soldiers were deployed to block its entry.
Israel's disengagement plan the evacuation of over 8,000 Israelis from 21 heavily-fortified settlements in the Gaza Strip, and hundreds more from four settlements in the northern West Bank.
Israel has occupied Gaza, the West Bank and East Jerusalem since 1967.