''I will exercise my mandate and authority where and when they are needed to protect the higher interests of the Palestinian people,'' Abbas wrote to Ismail Haniyeh, Hamas's prime minister-designate, in a letter copied to reporters.
The Palestinian Legislative Council is to convene on Monday for a confidence vote on the 24-member cabinet. Ratification is seen as certain given the Hamas majority in parliament after it swept January elections in the West Bank and Gaza Strip.
Haniyeh said his government would be sworn in by Wednesday.
The president is empowered by law to fire Haniyeh if his policies are deemed harmful to the national interest.
Formally committed to the Jewish state's destruction, Hamas is rejected as a peace partner by Israel and much of the West and Abbas, whose long-dominant Fatah faction seeks a Palestinian state alongside Israel, has appealed for Hamas to change.
AVOIDED CONFRONTATION Abbas has previously avoided confrontation, resisting foreign pressure to crack down on Hamas and other factions waging a more than 5-year-old Palestinian revolt for fear of civil war.
''Once your government assumes its responsibilities I ask you again to ... make the necessary corrections to your programme,'' the president said in his letter to Haniyeh.
Though it masterminded more than 60 suicide bombings during a Palestinian revolt that erupted in 2000, Hamas has largely abided by a ceasefire declared last year and has said it could extend the truce if Israel ends military crackdowns.
Faced with the threat of international aid cut-offs to the cash-strapped Palestinian Authority, Hamas has also hinted it would accept temporary statehood in the West Bank and Gaza.
Haniyeh played down the prospect of a showdown with Abbas.
''We will resolve all political differences between the institutions of the presidency and the cabinet through dialogue, cooperation and understanding,'' he said.
''We do not seek to cause a constitutional crisis.'' Abbas said in an interview published yesterday that he had proposed back-channel talks with Israel that would effectively circumvent Hamas.
But Israel, which holds a general election on Tuesday, poured cold water on the idea.
''He (Abbas) has failed in the biggest challenge which faced him from the very outset: to combat terror. As a result of the failure of his government, Hamas has risen,'' said interim Prime Minister Ehud Olmert, the frontrunner candidate.
Olmert has threatened to set the Jewish state's permanent borders by 2010 if peacemaking remains frozen. While Israel quit Gaza last year, Palestinians suspect it will cement a permanent hold on major Jewish settlement blocs in the West Bank.
Reuters SHR BD2341