Israeli Defence Minister Avigdor Lieberman has announced his resignation, citing his opposition to a ceasefire with Palestinian Islamist group Hamas.
Lieberman's party will withdraw from the conservative coalition government of Prime Minister Benjamin Netanyahu, raising the prospect of early elections.
Lieberman described an Egyptian-mediated deal with Hamas "a capitulation to terror".
This leaves Netanyahu with control of just 61 of the 120 seats in parliament a year before Israel’s next election.
Israeli political commentators had speculated that Netanyahu, who despite his approval ratings has been dogged by multiple corruption investigations, might bring forward the ballot.
But a spokesman for his rightist Likud party played down that option, saying Netanyahu would assume the defence post.
Lieberman has spoken in favour of harsh Israeli military action against Hamas, even as the government authorised a Qatari cash infusion to the impoverished enclave last week and limited itself to air strikes rather than a wider campaigns during this week’s fighting.
Born in the former Soviet Union, Lieberman’s voter base is made up of fellow Russian-speaking immigrants, and rightists and secularists who share his hostility to Israel’s Arab minority and the religious authority wielded by ultra-Orthodox Jewish parties.