BAGHDAD — Some 10,000 U.S. M-16 rifles and other military supplies worth about $17.9 million arrived in Iraq this week as U.S. troops pushed ahead with training and supplying Iraqi security forces battling “Islamic State” fighters, the Pentagon said on Tuesday.

The update on U.S. efforts to arm Iraqi troops followed an unusual detailed briefing last week on preparations for an operation this spring to retake Iraq’s second biggest city, Mosul, from “Islamic State” militants.

Pentagon spokesman Army Colonel Steve Warren said 10,000 red-dot optical sights and 100,000 ammunition magazines were also sent to Iraq, part of an expedited foreign military financing deal that was completed in 22 days, a quarter the normal time.

Thousands of Kevlar helmets and body armor plus 250 armored, mine resistant vehicles were delivered to Iraq in January. Warren said the United States sent 232 Hellfire missiles to Iraqi forces on Feb. 15, adding to the 1,570 sent last year. He said radios for the armored vehicles would arrive next month.

Last week, an official at the U.S. military’s Central Command told reporters that American and coalition troops would soon begin training Iraqi forces who are due to participate in the assault to retake Mosul. The official said an Iraqi and Kurdish force of 20,000 to 25,000 was needed for the offensive, which could take place as soon as April or May if troops were ready.

Republican Senators John McCain and Lindsey Graham have complained in a letter to President Obama that the military had “briefed our own war plans to our enemy.”

On Tuesday, Warren declined to comment on whether too much had been said at the briefing or to characterize it as a mistake.

“I think it was important that … CentCom (Central Command) conducted a briefing last week. It’s important that we’re as transparent as we can be with both the press and the American public so that they understand what … we’re trying to do,” he said.

Central Command has not regularly briefed on the campaign against “Islamic State,” other than to release figures about its daily air strikes.

Much of the information shared at the briefing had already been made public, either through testimony by officials in congressional hearings or in media reports on the conflicts in Iraq and Syria.

A coalition air strike in western Iraq killed at least 17 “Islamic State” militants overnight, a hospital source said on Thursday, and an Arabic TV channel said the group’s leader, Abu Bakr al-Baghdadi, had been in the area several hours before.

The channel, al-Arabiya al-Hadath, based its report on anonymous sources and gave no further information on Baghdadi. The report on his whereabouts could not be confirmed.