The momentum has shifted in the U.S.-led coalition fight against the Islamic State in Iraq and Syria, so it’s time to commit more forces for the looming battles ahead, the top U.S. civilian and military leaders told reporters Friday.

"We have a series of recommendations that we will be discussing with the president in the coming weeks to further enable our support for the Iraqi Security Forces, or ISF,” Chairman of the Joint Chiefs of Staff, Gen. Joe Dunford. “The secretary and I both believe that there will be an increase to the U.S. forces in Iraq in the coming weeks—but that decision hasn't been made.”

“We’re broadening both the weight and the nature of our attacks on ISIL,” added Defense Secretary Ash Carter. “In both Syria and Iraq, we're seeing important steps to shape what will become crucial battles in the months to come.”

Currently, the Pentagon says, there are 3,800 U.S. troops in Iraq for the coalition mission to destroy ISIS — although officials this week conceded that the figure doesn’t include “temporary” troops. The actual number tops 5,000, The Daily Beast’s Nancy Youssef reports.

The key near-term challenge remains the taking of Mosul, a city of 2 million and a key ISIS stronghold. U.S. officials say “several hundred” Marines are providing fire support to Iraqi security forces from Fire Base Bell, about 50 kilometers outside of Mosul. One Marine at the base was killed by an ISIS rocket on March 20; still, Dunford emphasized that base was behind the front lines.

“The primary force fighting in Mosul will be Iraqi security forces and we'll be in a position to provide advise, assist and enabling capabilities to make them successful,” he told reporters.

Both Carter and Dunford said that momentum in Iraq and Syria has shifted from ISIS toward the ISF and coalition forces.

Carter cited recent gains in Syria, like the seizure of the town of Shadadi — “a key connection between Raqqa and Mosul,” he said — by Kurdish forces aided by U.S. special operators.

Dunford’s assessment: “I think there's a lot of reasons for us to be optimistic about the next several months. But by no means would I say that we're about to break the back of ISIL or that the fight is over.”

Lt. Gen. Vincent Stewart, the head of the Defense Intelligence Agency recently testified that clearing Mosul could take a year or longer.

ISIS Number 2 Believed Killed

Carter also said Friday that he believes the U.S. military killed the Islamic State’s second-in-command, a man by the name of Haji Imam.

“The U.S. military killed several key ISIL terrorists this week, including, we believe, Haji Imam, who was a senior leader serving as a finance minister and who also is responsible for some external affairs and plots.”

Considered to be the next-in-line to succeed ISIS leader Abu Bakr al-Baghdadi, Imam’s real name is Abd al-Rahman Mustafa al-Qaduli, according to Middle East analyst Charles Lister. He previously served as Abu Musab al-Zarqawi’s deputy and later al-Qaeda in Iraq’s emir of Mosul. The U.S. Treasury Department guessed his age to be close to 60 when it designated him a wanted terrorist nearly two years ago.

"We are systematically eliminating ISIL's cabinet," Carter said. He also announced a strike on another senior leader believed to have paid ISIS fighters in Iraq, Abu Sarah. But according to Micah Zenko of the Council on Foreign Relations, the Pentagon has claimed to have killed some 120 ISIS senior leaders of varying ranks, making it “hard to know [the] importance of any one additional leader.”

Carter refused to elaborate any further. “I'm going to ask you,” he said, “to respect the fact that we're not going to go into any further details about how our coalition conducted the operations I mentioned earlier. Any more details than that could put lives and our future operations at risk, hinder the effectiveness of our campaign.”

However, anonymous U.S. defense officials told The Daily Beast the strike against Imam took place inside Syria. The U.S. and coalition jets have carried out 26 strikes in Syria over the past week, according to U.S. Central Command. That includes one near Palmyra, where Syrian troops backed by Russian forces, are advancing on the city ISIS has controlled since May.