Sens. Rob Portman (R-Ohio), Jeanne Shaheen (D-N.H.), Dick Durbin (D-Ill.), Richard Blumenthal (D-Conn.) and Ron Johnson (R-Wis.) wrote a letter Tuesday to Office of Management and Budget Director Mick Mulvaney after Politico reported that the administration was delaying the aid.
They wrote that the funds have helped Ukraine develop its own military capabilities and maintain its sovereignty as it faces Russian attacks.
"In fact, Ukraine continues to fight daily on its eastern border against Russia-backed separatists in the provinces of Donetsk and Luhansk, and over 10,000 Ukrainian soldiers and civilians have lost their lives in this war," they wrote. "U.S.-funded security assistance has already helped turn the tide in this conflict, and it is necessary to ensure the protection of the sovereign territory of this young country, going forward."
"This funding is crucial to the long term stability of Ukraine and has the continued backing and approval of the U.S. Congress which appropriated these funds. We strongly urge you to direct the Department of Defense to obligate these funds immediately," the senators added.
A Defense Department spokesperson told The Hill that the U.S. was working with Ukraine's government and the Multinational Joint Commission to evaluate the specific needs of Ukraine's armed forces.
The spokesperson added that the department does not publicly comment on internal budget deliberations.
The Hill has reached out to the Office of Management and Budget for comment.
President Trump asked officials to review the funding to make sure that it is being used to further U.S. interests, Politico reported last week, citing a senior administration official. Those asked to review the funding reportedly include Defense Secretary Mark Esper and national security adviser John Bolton.
President Trump has recently faced scrutiny over statements about Russia. He said last month that he would he would "certainly" invite Russian President Vladimir Putin to the next Group of Seven summit. Russia was expelled from what was then the Group of Eight because of its annexation of the Crimean Peninsula from Ukraine in 2014.