The U.S. State Department said on Monday that leaking of the Palestinian documents containing offers of major concessions to Israel will make the Middle East peace efforts more difficult, despite the American pledge to continue to broker for peace.

"We don't deny that this release will at least for a time make the situation more difficult than it already was," said State Department spokesman Philip Crowley.

"But we are clear-eyed about this. We always recognize that this would be a great challenge," he said.

British newspaper The Guardian and the Al-Jazeera news channel on Sunday published more than 1,600 documents that supposedly detail the behind-the-scenes notes and thinking of the Palestinian negotiating team in talks with then Israeli prime minister Ehud Olmert in 2008.

The documents showed that the Palestinians offered Israel major concessions on the thorny issues of annexed East Jerusalem and refugees in 2008 peace talks.

In a bid to play down the potentially serious fallout, Crowley insisted the "overall objective" of the Middle East peace process remains unchanged and a framework agreement is both "possible and necessary."

"It doesn't change our understanding of the challenge, and it doesn't change our pursuit of a framework agreement. We're going to continue to engage with the parties ... and continue to move them towards a framework agreement," he said.