The agreement, confirmed by Tourism Minister Yariv Levin to public radio and Lieberman's spokesman to AFP, will expand Prime Minister Benjamin Netanyahu's coalition to 66 lawmakers and make Lieberman defence minister.
Lieberman's spokesman said the deal would be signed in parliament, at 0800 GMT.
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Besides Lieberman becoming defence minister and another member of his party becoming immigrant absorption minister, the government agreed to allocate approximately 1.4 billion shekels ($363 million, 325 million euros) to pensions of elderly Israelis, including immigrants from the former Soviet Union, Lieberman's largest support base.
"These are the two major issues that are important to our constituency, and significant achievements," Lieberman's spokesman told AFP.
Netanyahu has sought to ease fears over Lieberman's expected appointment, saying he will continue to seek peace with the Palestinians and oversee the defence ministry's policies, which include control over the occupied West Bank.