John Kerry, US President Barack Obama's nominee for secretary of state, has said that should he be appointed he would push for a revival of the Israeli-Palestinian peace talks during his confirmation hearing.
Kerry was questioned by the Senate Foreign Relations Committee, which he has chaired for the past four years.
"We need to try to find a way forward, and I happen to believe that there is a way forward," Kerry, who will replace Hillary Clinton, told the committee on Thursday.
"But I also believe that if we can't be successful, the door, window ... to the possibility of a two-state solution could shut on everybody, and that would be disastrous in my judgment," he said.
The peace talks between Israel and Palestine broke down in 2010.
Kerry, 69, a five-time Massachusetts senator, also stressed his commitment to Obama's policy of seeking a diplomatic solution to persuade Iran to give up its suspected pursuit of nuclear weapons.
Tehran says its programme is solely for peaceful purposes.
"He [Obama] and I prefer a diplomatic resolution to this challenge and I will work to give diplomacy every effort to succeed," Kerry said. "But no one should mistake our resolve to reduce the nuclear threat."
Kerry said "everybody's very hopeful that we can make some progress on the diplomatic front now" and that Obama had made clear his willingness to have direct negotiations with Iran if need be.
On Syria, Kerry said there was a moment where Bashar al-Assad, the president, impelled partly by his desire to find jobs for his "burgeoning" youthful population, had an interest in improving relations with the US, but that he missed the opportunity.
"He has made a set of judgments that are inexcusable, that are reprehensible and I think is not long for remaining as the head of state in Syria," he said.
Kerry visited Damascus repeatedly before the outbreak of the country's devastating civil war and was a proponent of US re-engagement with the Syrian president.
Kerry, the Yale-educated son of a foreign service officer, said the "first priority" in protecting his credibility as a diplomat was the country's ability to get its fiscal house in order.
"Foreign policy is economic policy," Kerry told the Senate Foreign Relations Committee.
"It is urgent that we show people in the rest of the world that we can get our business done in an effective and timely way."
Obama nominated Kerry last month to replace Secretary of State Hillary Clinton, one of the most popular and visible members of his cabinet.
The Vietnam war veteran was the Democrats' 2004 presidential nominee, losing to Republican nominee George W Bush.
The Senate will hold a confirmation vote on Kerry on Tuesday, said Senate Majority Leader Harry Reid, a Democrat.
Kerry was praised by Republicans as well his fellow Democrats during the three and half hour hearing, and many of them said they were certain of his confirmation.
Republicans in particular said they appreciated his calls for fiscal order.
"I look at you, in being nominated for this, as someone who has almost led their entire life, if you will, for this moment, being able to serve in this capacity," said Senator Bob Corker of Tennessee, the leading Republican on the panel.