Prime minister of the Hamas-led Palestinian Authority Ismail Haniyeh sent a letter to PA President Mahmoud Abbas on Friday urging him not to go ahead with a referendum on establishing a Palestinian state alongside Israel.
He said the referendum would divide the Palestinian people and instead proposed forming a unity government with Fatah.
Abbas is eager to restart stalled peace talks with Israel, and on Saturday was expected to formally announce a July 31 date for the referendum. An official close to Abbas said late Friday the president would make his announcement as planned on Saturday.
Public opinion polls show the two-state proposal enjoys widespread support.
But an angry backlash after Friday's killings could erode Abbas' support. Crowds chanted anti-referendum slogans during Friday's Hamas demonstrations.
Abbas has endorsed the referendum plan as a way to end international sanctions against the Palestinians and restart peace talks.