US Secretary of State John Kerry warned Wednesday that time was slipping away to reach a Middle East peace deal, stressing for the first time that there may only be a year or two left.

Appearing before US lawmakers for the first time since becoming America's top diplomat in February, Kerry said his three trips to the region already were proof of his commitment to try to find a way to resume peace talks.

The Obama administration is "trying to find out what is possible," Kerry told the House Foreign Affairs Committee, as he laid out the State Department's priorities for the 2014 budget.

He stressed he had no plan so far to present to Congress "because we're in the process of working that out with the critical parties."

"But I can guarantee you that I am committed to this, because I believe the window for a two-state solution is shutting. I think we have some period of time -- a year to year-and-a-half to two years -- or it's over," Kerry warned.

Kerry, who has just returned from his fourth overseas trip during which he traveled to both Israel and the Palestinian territories, said he had found on both sides "a seriousness of purpose, a commitment to explore how we actually get to a negotiation."

"We all have some homework to do. We're doing that homework. And I ask you simply give us a little bit of time here," he added.

The top US diplomat is currently working on a plan to try to boost the Palestinian economy as part of efforts to restore trust between the two sides.

He told the House Appropriations Committee later that former British prime minister Tony Blair, the special envoy for the Middle East Quartet, had agreed to take on the job to try to "move the economics of the Palestinian Authority forward... a quantum leap."

The CEO of Coca-Cola, Muhtar Kent, had also agreed to be involved, Kerry said.

The Middle East Quartet is a diplomatic effort to mediate the peace process that includes Russia, the United Nations, United States and European Union.

"We're going to bring people to the table who have the ability to do transformative change and try to move the economy," Kerry told lawmakers.

But he stressed this plan was not alternative to the peace process. Instead, it was "a complement, supplementary effort to try to change the quality of life... and give you the political space to move on the other parts of this."