A standoff between Ukraine’s defense minister and the official in charge of procuring weapons threatened to escalate on Monday, stirring dissent in the government at a critical time as it seeks to persuade President Trump to maintain American support in its war with Russia.

The dispute erupted three days ago when the minister, Rustem Umerov, said he would not renew the contract of the official, Maryna Bezrukova, citing “unsatisfactory” results. But on Monday, Ms. Bezrukova said she would remain in her position, pointing out that her contract had been renewed by her agency’s supervisory board and that Mr. Umerov had no right to override that decision.

The agency was established to ensure transparency and efficiency in acquiring arms. Activists and some lawmakers, including a prominent one in President Volodymyr Zelensky’s party, denounced Mr. Umerov’s move as an abuse of power undermining anticorruption efforts.

“The minister’s action is a serious offense against our legislation and corporate governance,” Ms. Bezrukova said in an interview over the weekend, calling it an “attack” on the agency’s efforts to cut out questionable intermediaries Ukraine has sometimes relied on to buy weapons during the war.

She reported to her office on Monday, and it was unclear how the standoff would be resolved.

The dispute threatens to weaken an organization that managed over $7 billion in weapons procurement last year and has become a partner for Western allies channeling funds into Ukraine’s growing defense industry — a new initiative aimed at developing an alternative for dwindling arms supplies from the West.

After meeting with government and agency officials in Kyiv on Monday to discuss the standoff, diplomats from the Group of 7 nations urged in a statement that the situation “be resolved expeditiously and focus on keeping defense procurement going.” It said that “consistency with good governance principles and NATO recommendations is important to maintain the trust of the public and international partners.”

The head of the Ukrainian Parliament’s anticorruption committee has called for the defense minister’s resignation, but it seems unlikely that he will resign, as Mr. Zelensky has not offered any criticism so far. Mr. Umerov did not respond to a request for comment.

This is not the first time the Ukrainian government has moved to oust officials with responsibility for reforming state institutions, some of whose efforts have caused internal friction.

But the attempt to dismiss Ms. Bezrukova comes as Ukraine is struggling to send enough weapons to troops at the front trying to fend off the Russian invasion that began in 2022 and faces the risk of losing vital arms supplies from its key ally, the United States. Activists are also concerned that it sends the wrong message to Western partners who have expressed concerns about corruption in Ukraine.

“What minister Umerov is doing is sabotaging our defense capabilities and our ability to keep the trust of our international partners regarding weapons procurement,” said Daria Kaleniuk, the executive director of Ukraine’s Anti-Corruption Action Center, a group dedicated to rooting out public graft that is now focused on war profiteering.

Mr. Umerov said in a post on Facebook that the agency had failed in the “timely supply of ammunition to our army” and had instead become embroiled in “political games, leaks of contracts, and leaks of information.” He did not provide specific examples.

Tamerlan Vahabov, a former adviser to Ms. Bezrukova who resigned last year, has also criticized the agency, saying it had sometimes failed to effectively evaluate contracts. He said the agency leaned too heavily on purchasing from state companies instead of private suppliers.

Ms. Bezrukova was appointed a year ago, after Mr. Umerov took over as defense minister, and promised to root out corruption in the ministry following a series of revelations about mismanaged contracts for weapons and basic supplies such as food.

The main task of Ms. Bezrukova, a former top manager at the national electricity company, was to eliminate intermediaries, often shady arms dealers who were inflating prices. She said the agency had reduced Ukrainian intermediaries’ share of procurements from 81 percent in 2023 to just 12 percent last year. These figures could not be independently verified.

Ms. Bezrukova said her work led to tensions with the ministry. She claimed that defense officials pressured her to sign a contract with a state-owned Ukrainian weapons factory that lacked the workers and gunpowder to produce mortar shells. Many of the shells failed to fire after being sent to the front setting off a major scandal in Ukraine.

Mr. Vahabov said that even if she faced pressure, Ms. Bezrukova should have been more vocal in opposing the contract. He also said that she could have conducted more due diligence controls of production of the weapons at the factory.

Ms. Bezrukova said she had hoped that the creation of a supervisory board at the agency late last year, a move applauded by Western partners, would help safeguard her independence. “I don’t want to be window dressing or a reputational washing machine,” she said in the interview Saturday.

However, a day before the board’s first meeting, on Dec. 17, the defense ministry amended the agency’s charter, effectively granting the ministry final authority over most of the board’s decisions. “They de facto sterilized the board’s authority,” said Yuriy Dzhygyr, the chairman of the board.

After the supervisory board voted last week to extend Ms. Bezrukova’s contract for one year, Mr. Umerov said he would not renew her contract and announced the dismissal of two state representatives on the board, including Mr. Dzhygyr.

Ms. Kaleniuk, the anticorruption activist, said the charter did not grant the defense ministry a say in extending the agency head’s contract. The charter, reviewed by The New York Times, does, however, allow the defense ministry to dismiss any agency official “in the event of identified existing or potential threats to Ukraine’s national security.”

It remains unclear on what legal grounds Mr. Umerov decided to fire Ms. Bezrukova.

On Monday, Ukraine’s National Anti-Corruption Bureau opened an investigation into Mr. Umerov over accusations of abuse of power. The inquiry follows a complaint filed by the Anti-Corruption Action Center, according to a letter from the bureau to the group, which was shared with The Times by Ms. Kaleniuk.

With Western partners unable to supply all the weapons Ukraine needs, the agency has helped enact an initiative that uses Western funds to pay for contracts signed with local arms manufacturers. The defense ministry said that more than half a billion dollars’ worth of weapons were produced through this new mechanism last year.

Whether that will still happen is unclear.

The German Marshall Fund of the United States, a research institution, raised concerns about the Ukrainian infighting.

“This is the worst possible time,” it said in a statement, “for Kyiv to turn back the clock on a defense reform success story: when Ukraine needs additional funding for weapons and cynical opponents in Moscow and in certain quarters of Washington are looking for reasons to cast doubt upon the integrity of Ukrainian defense governance.”

Andrew E. Kramer contributed reporting.