Israeli and Palestinian officials have put forward clashing formats for peace talks, which are due to resume in Washington for the first time in nearly three years.
After intense mediation, US Secretary of State John Kerry plans to bring the negotiators together this evening and tomorrow.
He said he was seeking "reasonable compromises" in the talks.
"Going forward it is no secret this is a difficult process. If it were easy, it would have happened a long time ago," Mr Kerry told reporters.
"It is no secret, therefore, that many difficult choices lie ahead for the negotiators and for the leaders as we seek reasonable compromises on tough, complicated, emotional and symbolic issues."
US President Barack Obama has welcomed the resumption of negotiations as a promising step but says that hard choices remain ahead.
Mr Kerry announced Martin Indyk, a former US ambassador to Israel, as Washington's Middle East envoy, whose job will be to oversee the negotiations.
Mr Indyk is a veteran of US efforts to resolve the Israeli-Palestinian conflict.
He was a senior official in the Clinton administration, which oversaw a failed summit in 2000 after which violence erupted in Israel and Palestinian territories.
This time "all of the issues that are at the core of a permanent accord will be negotiated simultaneously", Silvan Shalom, a member of Israeli Prime Minister Benjamin Netayahu's cabinet and Likud party, told Israel's Army Radio.
Yasser Abed Rabbo, a senior official in Palestinian President Mahmoud Abbas's Palestine Liberation Organisation, said the US letter of invitation to the Washington talks had not specified which disputes were to be discussed.
But Mr Abed Rabbo told Voice of Palestine radio the talks "will begin, in principle, on the issues of borders and security".
Mr Netanyahu says any peace accord must safeguard Israel, which has often clashed with Hamas in Gaza and fears the Islamist movement could gain ground in the West Bank.
Mr Kerry has also described Israel's security as "paramount".
After months of intensive and discreet mediation, Mr Kerry announced on 19 July in Amman, Jordan, that the parties had laid the groundwork to resume negotiations on the so-called "final status" issues that must be resolved to end the dispute.
