Barack Obama has clarified what he meant by his call for a two - state solution along 1967 lines with mutually agreed land exchanges.

The remark, made during his major Middle East address last week, was said to represent a more extreme statement on Israel than that of any previous administration. Critics, including Israel's prime minister Binyamin Netanyahu, called it unacceptable and rejected the idea of a return to an Israel that was just nine miles wide.

But the President, addressing the American Israel Public Affairs Committee's annual conference on Sunday, said that if there was a controversy, then it was not one "based in substance".

He said: "By definition, it means that the parties themselves - Israelis and Palestinians - will negotiate a border that is different from the one that existed on June 4, 1967."

He said that it was a proposal long acknowledged privately by those who were working on the peace process. He added: "It allows the parties themselves to account for the changes that have taken place over the last forty-four years, including the new demographic realities on the ground and the needs of both sides."

President Obama acknowledged that what he was asking was a hard choice but urged against intransigence on the part of the Israelis, the Palestinians, the Arab States, and the international community.

He said: "We cannot afford to wait another decade, or another two decades, or another three decades, to achieve peace. The world is moving too fast.

"As a friend of Israel, I am committed to doing our part to see that this goal is realised."