John Kerry, US secretary of state, has met Benjamin Netanyahu, the Israeli prime minister, to push for a framework for Middle East peace talks.
The two leaders met in Jerusalem on Thursday, marking the start of what is expected to be an intense four days of back-and-forth diplomacy between Israeli and Palestinian leaders.
"The time is soon arriving where leaders are going to have to make difficult decisions. We are close to that time, if not at it," Kerry said before meeting Netanyahu.
Kerry said that if both sides could agree on a framework for peace talks, a "breakthrough" will have been made.
"I plan to work with both sides more intensely in these next days to narrow the differences on a framework that will provide the agreed guidelines for permanent status negotiations," he said.
"This is not mission impossible."
Kerry has faced fierce opposition, due to irreconcilable demands on both sides, since negotiations reopened after a three-year hiatus.
Netanyahu said he does not believe the Palestinians are taking the process seriously.
"A few days ago in Ramallah, [Palestinian] President [Mahmoud] Abbas embraced terrorists as heroes. How can he say that he stands against terrorism when he embraces the perpetrators of terrorism and glorifies them as heroes?" Netanyahu said.
He was referring to Israel's release of the third of four batches of 104 Palestinian prisoners as a goodwill gesture agreed upon under the peace talks.
A senior Israeli cabinet minister and more than a dozen legislators also poured cement at a construction site in an illegal settlement in the West Bank's Jordan Valley on Thursday to send a strong message to Kerry that Israel will never relinquish the area.
Israel wants to keep existing settlements built inside occupied Palestinian territory.
But Palestinians want borders based on lines that existed before 1967, when Israel captured the West Bank and East Jerusalem during the Six-Day War.
Kerry and his team hope to lock down a framework as soon as possible to address issues like the borders of a future Palestinian state, Palestinian refugees and the fate of Jerusalem, which both sides claim as their capital.
Kerry has made 10 visits to Israel since March 2013.
Both sides have continued to accuse each other of lacking dedication to achieve a lasting peace.