BRUSSELS — Defense Secretary Ashton B. Carter said Wednesday that he has ordered the Pentagon to suspend its efforts to collect payments from California Army National Guard soldiers who were told to return their enlistment bonuses.

Carter announced steps to resolve the cases of thousands of soldiers who collectively received millions of dollars in bonuses at the height of the wars in Iraq and Afghanistan, but then were told years later that the money had to be repaid.

In a statement, Carter said he had ordered the Pentagon’s financial department to stop the payment collection until measures can be put in place to provide the affected service members with the support they need to appeal the process.

“There is no more important responsibility for the Department of Defense than keeping faith with our people. That means treating them fairly and equitably, honoring their service and sacrifice, and keeping our word,” Carter said in a statement. “Hundreds of affected Guard members in California have sought and been granted relief. But that process has simply moved too slowly and in some cases imposed unreasonable burdens on service members. That is unacceptable.”

While the Pentagon has said that up to 10,000 California National Guard soldiers may have been affected, dozens of other National Guard soldiers throughout the country received similar payments. The instances affecting the California National Guard were first reported by the Los Angeles Times on Saturday. Some of the cases have been subject to a criminal investigation that started when recruiters promised bonuses to soldiers, even though they were not authorized to do so.

Carter’s announcement comes after several days of members of Congress calling on him to act. On Monday, the House Committee on Oversight and Government Reform opened an investigation and requested all documents associated with the California cases. The panel also asked senior officers with the California Army National Guard and the National Guard Bureau to brief committee members by Nov. 17.

Carter has assigned Peter Levine, the top personnel official at the Pentagon, to assess the situation and to create a process that can resolve all of the payment cases by July 2017.

“Our goal is to have a process that honors the commitment to our service members and also to our responsibility of the taxpayer,” Carter told reporters Wednesday.

He added that he hadn’t ruled out that some of the service members might still have to repay their bonuses, saying that “under the law, we have to keep that option open.”

Levine, speaking to reporters at the Pentagon, said the Defense Department’s intent is to jump-start the review process to taking months, not years. The Pentagon will “surge” additional personnel to review cases, but doesn’t intend to change anything permanent in how it reviews collection cases.

“Once we’re doing working through this California block of cases, we will presumably revert to the existing processes,” Levine said.

Levine said that about 14,000 soldiers in California were initially cited as potentially receiving inappropriate payments. The Guard in California ultimately cleared about 4,000 of those cases, leaving about 10,000 more who could be affected. The Pentagon has been withholding payment from about 2,000 of those soldiers.

Affected service members can receive refunds, but the Defense Department does not have the ability to assist them with other effects that may have occurred, such as bankruptcy and credit loss. The Pentagon also is searching for how to reach Guard members who have left the force and have changed addresses, Levine said.

Maj. Gen. Matthew Beevers, the No. 2 officer in the California Army National Guard, said Monday that by law, the Guard does not have the ability to stop the collection effort and sought help from Congress two years ago to provide relief to affected soldiers. That effort stalled, in part because the Congressional Budget Office deemed it expensive, Beevers said.

But Capitol Hill officials have questioned how well the Guard communicated the problem. One House official, speaking on the condition of anonymity, said that the problem was brought up in an email to congressional staff, but never was raised in person.

“If this was such an urgent matter they should have known more outreach was needed,” the official said.

Lawmakers were quick to address Carter’s remarks Wednesday. Rep. Vern Buchanan (R-Fla.) called Carter’s new measures “not good enough” and said there was “no middle ground” on the issue.

“The Pentagon needs to tell veterans it will permanently — not temporarily — end its obscene effort to collect enlistment bonuses from a decade ago,” he said.

Rep. Adam B. Schiff (D-Calif.) said that Carter made the right call in suspending collection efforts, but that more needs to be done, beginning with the passage of legislation that waives the debts and provides financial relief to soldiers who have already repaid some or all of what the Pentagon said they owed.

“It should not fall on the shoulders of those who serve our country to pay for the mistakes of others that offered these incentives improperly or allowed the error to go undiscovered for so many years,” Schiff said. “I continue to work on drafting legislation that will accomplish these goals, and hope to introduce it in the coming weeks before Congress comes back into session.”

Rep. Duncan D. Hunter (R-Calif.) said that Carter’s decision was the “only action to take,” but questioned why it took so long.

“It shouldn’t be lost on anyone that the secretary is taking this action through existing authority and that same authority could have been exercised at any point since the size and scope of the situation was realized,” he said.

House Majority Leader Kevin McCarthy (R-Calif.) is expected to host a bipartisan conference call with Deputy Defense Secretary Robert O. Work on Wednesday night to address long-term plans to fix the problem. Levine said that the Pentagon does not believe it needs legislation to address the issues.

This story was initially published at 10:16 a.m. and updated with reporting from the Pentagon.

Thomas Gibbons-Neff reported from Brussels. Lamothe reported from Washington.