President Barack Obama warned America's pro-Israel lobby on Sunday that the Jewish state will face growing isolation without a credible Middle East peace process. He defended his endorsement of a future Palestine based on Israel's 1967 boundaries but subject to negotiated land swaps as a public expression of long-standing U.S. policy.

After a contentious couple of days, Obama sought to alleviate concerns that his administration was veering in a pro-Palestinian direction by placing Thursday's major Mideast policy speech in the context of Israel's security. He told the American Israel Public Affairs Committee that the border lines he referred to reflected U.S. thinking dating back to President Bill Clinton, and that it needed to be brought out into the open.

"If there's a controversy, then it's not based in substance," Obama said in a well-received speech at a Washington convention center. "What I did on Thursday was to say publicly what has long been acknowledged privately. I have done so because we cannot afford to wait another decade, or another two decades, or another three decades, to achieve peace."