The outgoing Palestinian parliament has voted to give new presidential powers to Mahmoud Abbas, ahead of the swearing in of a new militant-led legislature.
Some Hamas members said the votes were like a bloodless coup
The Palestinian leader will be able to appoint a constitutional court that can cancel future legislation.
Hamas - the militant Islamic movement which won a landslide in January's poll - called the move illegitimate.
The outgoing parliament is dominated by members of the mainstream Fatah faction which is led by Mr Abbas.
MPs voted overwhelmingly to approve Mr Abbas' decree to create the constitutional court, made up of judges appointed by the Palestinian Authority president.
Before the amendment was passed, Palestinian law required that parliament must approve presidential appointments to the judiciary.
MPs also backed a decree which automatically makes members of the incoming parliament members of the Palestine Liberation Organisation's (PLO) parliament in exile, according to reports.
Unlike the Hamas charter, the PLO charter recognises the legitimacy of Israel.
MPs also approved plans to appoint a Fatah deputy, Mahmoud Abul Rob, as head of the Palestinian Authority's main financial watchdog, the AFP news agency reported.
Hamas members say they will work in order to cancel any 11th-hour legislation which they describe as "unconstitutional".
"This parliament has no mandate and no authority to issue any new legislation," said Said Siyam, an incoming Hamas MP from Gaza.
The new parliament, which will have 74 Hamas MPs out of 132, is due to be sworn in by Mr Abbas on Saturday.
Hamas says it has chosen a prime ministerial candidate from within its ranks, but it has not made the name public.
Analysts say a Hamas prime minister could complicate any Middle East peace efforts because Israel and the US say they will not talk to members of the group, which they consider a terrorist organisation.