WASHINGTON 

Republican Rep. Brian Fitzpatrick urged President Donald Trump on Wednesday to address his "serious concern" over reports that the US is withholding critical defense material pledged to Ukraine.

"I respectfully request an emergency briefing from the White House and the Department of Defense on the Pentagon’s recent review of our nation’s weapons and munitions stockpiles, as well as the decision to withhold urgent, lifesaving military assistance to Ukraine," Fitzpatrick wrote in a letter to the White House.

His letter came a day after local media reported that the Pentagon had suspended some shipments of air defense missiles and other precision munitions to Ukraine due to concerns over low US stockpiles.

"This comes as Russia launches the largest aerial assault since the war began, firing over 500 weapons at civilian targets in a single week. Ukrainian forces are not only safeguarding their homeland—they are holding the front line of freedom itself," Fitzpatrick said.

The Department of Defense said Wednesday that it continues to provide Trump with "robust options regarding military aid to Ukraine, consistent with his goal of bringing this tragic war to an end."

"At the same time, the department is rigorously examining and adapting its approach towards achieving this objective while also preserving US military readiness and defense priorities that support the president's America First agenda," chief Pentagon spokesman Sean Parnell told reporters.

The Pentagon will not be providing any updates to specific quantities or types of munitions being provided to Ukraine, or the timelines associated with these transfers, he added.

Ukraine warned Wednesday that delays or reductions in defense support "would only encourage" Russia to prolong its war.