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An aide to Palestinian President Mahmoud Abbas says the gaps between Israeli and Palestinian negotiators only have widened since talks began seven months ago.

U.S. Secretary of State John Kerry wants both sides to agree to a framework for a peace deal — effectively ground rules for future negotiations — by April 29.

Mohammed Ishtayeh, the Abbas aide and former negotiator, said Thursday the U.S. might seek an extension but that he doubts this will happen because of lack of common ground.

Ishtayeh says a key obstacle is Israel's demand that the Palestinians accept it as a Jewish state. He says Abbas can't do so "under any circumstance" because it would restrict rights of Palestinian refugees and Israeli Arabs.

Abbas is meeting March 17 with U.S. President Barack Obama.