A far-right Israeli minister has blasted a plan by the government of Prime Minister Benjamin Netanyahu to gradually expand military operations in Gaza, calling it a “foolish” half-measure that would undermine efforts to defeat the militant group.

Israel’s security cabinet approved a decision by a majority vote early Friday for the military to prepare to take control of Gaza City as a first step. But those preparations are expected to take weeks or months, potentially leaving open options for a diplomatic maneuver that would halt or reverse the military operation.

Bezalel Smotrich, Israel’s hard-line finance minister, said in a video statement on Saturday night that he did not support the decision. He called on Mr. Netanyahu to reconvene the security cabinet and pledge to go for a “sharp, clear path” to a decisive victory over Hamas with “no more stops in the middle.”

The comments by Mr. Smotrich could once again threaten the stability of Mr. Netanyahu’s increasingly fractious and tenuous coalition government. Mr. Smotrich and another right-wing minister, Itamar Ben-Gvir, have repeatedly vowed to leave the coalition if Mr. Netanyahu relented on his tough line on Gaza and Hamas.

Mr. Smotrich said that the prime minister had assured him of “a dramatic plan” to defeat Hamas by means of a “lightning-fast military victory.”

But Mr. Netanyahu had done an “about face,” he said, and along with the cabinet had “decided once again to do more of the same: launching a military operation that is not aimed at resolving the issue.” Instead, Mr. Smotrich added, the new plan’s objective was to pressure Hamas to agree to a partial deal that would usher in a temporary cease-fire and see hostages being held in Gaza exchanged for Palestinian prisoners in Israel.

Israel’s security cabinet deliberated for about 10 hours on Thursday night about how to proceed in Gaza, and released an ambiguous pre-dawn statement on Friday with few details.

The cabinet set a deadline of Oct. 7 for the military to complete the evacuation southward of the hundreds of thousands of Palestinian residents of Gaza City, before any military push into the city, according to an Israeli official who was speaking on the condition of anonymity to share details of the confidential discussion.

It will also take time for the military to call up enough reserve forces to carry out the mission, and the details of the plan could always change.

Mr. Smotrich has been pressing for Israel to impose sovereignty in Gaza and pave the way for renewed Jewish settlement there, 20 years after Israel withdrew its forces and evacuated all of its settlers from the enclave.

Oct. 7 is a symbolic date that will mark the second anniversary of the Hamas-led attack on Israel that ignited the war. About 1,200 people were killed in the attack, with 250 taken hostage, according to the Israeli authorities. More than 60,000 people have been killed in Gaza since the war began, according to health officials in the territory, who do not distinguish between civilians and combatants.

The risk for Mr. Netanyahu is that his latest plan could cost the lives of many more Palestinians and Israeli soldiers while also endangering the 20 hostages believed to still be alive.

Israel captured much of Gaza City, the main city in the enclave, in the first months of war, before relinquishing it all on the false assumption that the military had achieved operational control of the area.

Mr. Smotrich said that if Hamas were to agree to a deal, Israel would “retreat once again” and allow the militant group to recover and to rearm. He stopped short of saying he would resign but said he had “lost faith” in Mr. Netanyahu.

Tzvi Sukkot, a member of Mr. Smotrich’s Religious Zionism party, suggested on Sunday that it might be time to break with Mr. Netanyahu’s coalition and for Israel to go to an early election. The next election is currently scheduled for October 2026.

But Mr. Ben-Gvir, the leader of another far-right party on whose support Mr. Netanyahu relies, praised the plan to conquer all of Gaza City and said it would involve displacing 1 million Palestinians.

Myra Noveck contributed reporting from Jerusalem.