Ramallah, West Bank - Palestinian President Mahmoud Abbas's advisers are looking at options for holding new elections that could limit Hamas participation, Palestinian officials said on Wednesday.

One of these options would bar candidates from Hamas and other groups from participating unless they accepted Palestinian law and previous agreements signed by the Palestine Liberation Organisation (PLO).

Abbas's advisers, who spoke on condition of anonymity, stressed that no final decisions have been made.

Hamas, which won a majority of the seats in parliament in a January 2006 election, has said it would be unconstitutional for Abbas to call early parliamentary and presidential elections. The group has threatened to block any election effort.

The long-dominant Fatah faction of the PLO, then led by Yasser Arafat and now headed by Abbas, recognised Israel and dropped its commitment to "armed struggle" on signing interim peace accords with Israel in 1993.

Hamas refuses to renounce violence and says it will not recognise Israel as demanded by major Western powers.

Hamas leaders have offered a long-term truce with Israel in return for a Palestinian state in the occupied West Bank and the Gaza Strip.

Nimer Hammad, an aide to Abbas, said there was a "serious discussion" under way about how to hold parliamentary and presidential elections despite opposition from Hamas Islamists who seized control of the Gaza Strip in June.

"Until now, no position has been taken," Hammad said, but added: "Whoever wants to run for elections must abide by Palestinian law."

Another Abbas aide, who asked not to be identified, said: "There are preparations for elections and the president is now studying the options that are available to him."

Abbas told Reuters in a recent interview that he would decree a change in Palestinian electoral rules that might make it harder for Hamas to maintain the parliamentary majority won last year.

Abbas also said parliamentary and presidential elections must be held simultaneously in the West Bank and Gaza Strip -- a condition that leaves the timing uncertain, given the opposition of Hamas leaders.

Legislative elections are not scheduled until 2010 and some constitutional experts note that the Palestinian Basic Law, which functions as an interim constitution, has no provision for calling early elections.