The United States said on Wednesday it was disappointed by a unity pact agreed between the Hamas and Palestinian Authority President Mahmoud Abbas's Palestine Liberation Organization and said it could seriously complicate peace efforts.
"The timing was troubling and we were certainly disappointed in the announcement," State Department spokeswoman Jen Psaki told a regular news briefing.
"This could seriously complicate our efforts. Not just our efforts but the efforts of the parties to extend their negotiations."
Abbas said on Wednesday that the unity pact did not contradict peace talks he is pursuing with Israel.
Israel called off a session of talks in response to the deal with the Gaza-based Islamist group, which is sworn to its destruction. But Abbas said in a statement that an independent state living peacefully alongside Israel remained his goal.
Hamas and the PLO agreed on Wednesday to implement a unity pact, both sides announced in a joint news conference.
The move envisions forming a unity government within five weeks and holding national elections six months after a vote of confidence by the Palestinian parliament.
Channel 2 said Prime Minister Binyamin Netanyahu would convene an emergency session of his security cabinet on Thursday to discuss his response.
Palestinians have long hoped for a healing of the political rift between the PLO and militant Hamas, which won a Palestinian election in 2006 and seized control of the Gaza Strip from forces loyal to Western-backed Abbas in 2007.
But Arab-brokered unity pacts reached between the two sides have yet to be implemented, leaving many Palestinians skeptical about their leaders' reconciliation pledges.
"This is the good news we tell our people: the era of division is over," Hamas prime minister Ismail Haniyeh told Palestinian reporters to loud applause.
Hamas has repeatedly battled Israel, which it refuses to recognize. Before Wednesday's announcement, Israeli Prime Minister Benjamin Netanyahu cautioned Abbas over the unity efforts, saying he had to choose between peace with Israel or its Islamist enemy.