WASHINGTON – The U.S. and its allies last month dropped the fewest bombs on Islamic State in Iraq and the Levant targets in Iraq and Syria since June, even though defense officials say the campaign to defeat the terrorist group has been accelerating.

U.S.-led forces dropped 2,054 munitions last month, down from 2,694 in January and 3,139 in December, according to Air Force data. That's the fewest since 1,683 last June and reflects a continuing decline from a peak of 3,227 weapons dropped in November. A partial cease-fire went into effect in Syria on Feb. 27, but that agreement doesn't cover attacks on ISIL targets.

While Defense Secretary Ash Carter has said the drive against ISIL is gaining momentum, some Republican presidential candidates have called for more intensive bombing.

The number of "weapons dropped does not necessarily provide a 1-to-1 correlation for total pressure being applied" against ISIL, according to Army Maj. Roger Cabiness, a Defense Department spokesman. Intelligence gathered through reconnaissance sorties "enables the coalition to become increasingly effective at striking strategic targets that put intense pressure on" the militants, he said via e-mail.

The decline in munitions hasn't been mentioned publicly by Pentagon and Air Force officials. They have focused on the more than 55,000 combat sorties flown since the U.S.-led air campaign against ISIL began over Iraq in August 2014, a total that includes reconnaissance and surveillance flights and aerial refueling missions. Nor does U.S. Central Command disclose how many bombs are dropped in its daily summary.

Pentagon officials have said that the U.S. inventory of smart bombs has declined, but Cabiness said that hasn't affected the pace of bombing.

"We strike targets when and where we find them," Cabiness said. "There will be periods of time when these numbers vary because of factors such as weather, requirements for strike packages and the number of available targets."

The surge of munitions in November may have reflected air support for Iraq forces as they prepared for the successful campaign to retake Ramadi that began late that month, Chris Harmer, an analyst for the Washington-based Institute for the Study of War said in an e-mail. "If/when the long-rumored assault on Mosul commences, those numbers will spike again."

The U.S. has dropped fewer munitions per sortie against ISIL targets than in any operation since the Cold War ended because this campaign "has been extremely difficult to prosecute" Harmer said. Maneuvering in "small groups of dismounted infantry, largely unsupported by artillery, tanks, and fighting vehicles, makes it difficult for U.S. aircraft to accurately acquire targets," he said. That's been compounded by a lack of U.S. ground personnel functioning as target spotters, he said.

Republican Sen. Ted Cruz has called for more intensive air attacks on ISIL. Donald Trump has said that as president he would "bomb the hell out of" ISIL.