US President Barack Obama has said a push for unity with Hamas by Palestinian Authority leader Mahmoud Abbas was "unhelpful" but vowed the US would not give up trying to broker peace in the Middle East.

The proposed tie-up between Mr Abbas's Fatah and Hamas prompted Israeli Prime Minister Benjamin Netanyahu to halt peace talks on the grounds Hamas wanted to "liquidate" Israel.

Mr Obama backed the Middle East peace drive by his Secretary of State John Kerry and said he would keep trying to coax Israelis and Palestinians through the door to peace.

"The fact that recently President Abbas took the unhelpful step of rejoining talks with Hamas is just one of a series of choices that both Israel and the Palestinians have made which are not conducive to solving this crisis," Mr Obama said.

"There comes a point at which there just needs to be a pause and both sides need to look at the alternatives."

The president hinted that his administration may expend less energy on the talks than in recent months, but did not rule out a return to Middle East peacemaking entirely.

"Realistically, there is one door and that is the two parties getting together to make some very difficult compromises," Mr Obama said.

"We will continue to encourage them to walk through that door. Do I expect they will walk through that door, next week, next month or even in the course of the next six months? No."

The two sides have been on a collision course since March when Israel refused to release a batch of Palestinian prisoners in line with the US-brokered agreement on resuming the talks.

The Palestinians retaliated by applying to join 15 international treaties and then Mr Abbas, who heads the Palestinian Authority and Fatah, listed conditions for talks beyond an 29 April deadline.

Israel and the US were hoping to extend the talks beyond the deadline, having failed to achieve any concrete results so far.