Israel's Prime Minister Benjamin Netanyahu struck a surprise deal with the opposition Kadima party early Tuesday, drawing them into his government just days after he called for an early election.

Kadima agreed to a deal in which its leader Shaul Mofaz would become deputy prime minister and a minister without portfolio in the new cabinet, public radio reported.

Details of the agreement were still to be finalised, said the report.

But they included an understanding that Kadima would back Netanyahu in return for changes to a contentious law that allows ultra-Orthodox Jews to defer their military service.

Zehava Galon, leader of the left-wing Meretz party, denounced the deal as a cynical political manouevre.

On Sunday, Netanyahu had called for early elections, saying he wanted to avoid a year and a half of political instability. Even on Monday morning, he told his weekly cabinet meeting that he wanted an election on September 4.

But this new deal effectively cancels Monday's moves by the Knesset, Israel's parliament, to clear the way for the election Netanyahu had said he wanted by voting for the dissolution of its current session.

The current parliament's mandate runs until October 2013.