Hamas has signed a pledge to back any Palestinian bid to join the International Criminal Court, two senior officials in the group said today.
Such a step could expose Israel as well as Hamas to war crimes investigations.
Palestinian President Mahmoud Abbas has debated for months whether to join the court, a step that would transform his relations with Israel from tense to openly hostile.
Last month, Abbas obtained written pledges of support from his Fatah movement and other factions in the Palestine Liberation Organisation, and said he would also seek the formal backing of Hamas, his main political rival.
Hamas said for several weeks that it was studying the idea. If Abbas were to turn to the court, Hamas could be investigated for its indiscriminate rocket fire at Israel for more than a decade, while Israel could come under scrutiny for its actions in the current Gaza war as well as its settlement building on war-won lands.
In last two days, Abbas held meetings in Qatar with the top Hamas leader in exile, Khaled Mashaal.
Early today, a senior Hamas leader, Moussa Abu Marzouk, wrote on his Facebook page that "Hamas has signed the paper" of support Abbas had requested.
Another Hamas official, Izzat Rishq, confirmed the document was signed. Abu Marzouk's post was reported on Hamas news websites.
Abu Marzouk and Rishq did not explain Hamas' reasons for agreeing to support a Palestinian membership bid.
There was no comment from Abbas aides and no immediate reaction from Israel, which has opposed involving the court.
Turning to the International Criminal Court became an option for Abbas in 2012, after the UN General Assembly recognized "Palestine" in the West Bank, Gaza and east Jerusalem, lands captured by Israel in 1967, as a non-member observer state. The upgrade to a state opened the door to requesting the court's jurisdiction in Palestine.