Jeff Bezos, president and chief executive officer of Amazon.com Inc., right, speaks as U.S. President Donald Trump, left, and Satya Nadella, chief executive officer of Microsoft Corp., listen during the American Technology Council roundtable hosted at the White House in Washington, D.C., U.S., on Monday, June 19, 2017.

A group of Republican lawmakers wrote a letter Thursday asking President Donald Trump not to delay the awarding of a Pentagon cloud contract.

Trump said Thursday he would "look very closely" at the contract, which is believed to be worth up to $10 billion and is expected to be awarded to either Microsoft or Amazon.

Four members of the House Armed Services Committee, including ranking member Rep. Mac Thornberry, R-Texas, said moving forward with the contract was critical to U.S. national security interests.

"We believe it is essential for our national security to move forward as quickly as possible with the award and implementation of this contract," according to the letter, which was sent on Thursday. "It meets only a portion of the Department of Defense's needs for the cloud, but it is an important first step."

"Moving to the cloud will help DOD operate faster, more efficiently, and compete with adversaries, like China," the letter said.

In April, IBM and Oracle were ruled out for the cloud-computing contract, known as the Joint Enterprise Defense Infrastructure, or JEDI, leaving Amazon and Microsoft as the only remaining competitors for the contract.

The companies have been competing head-to-head to win the contract as they work to expand their respective cloud businesses.

The DOD was supposed to award a recipient of the contract in September 2018. The contract is now expected to be awarded as soon as next month, the Pentagon told CNBC.

Trump said he would examine the JEDI contract after receiving complaints from other companies, including Microsoft, Oracle and IBM. Trump has previously sparred with Amazon CEO Jeff Bezos over a number of issues, notably his ownership of The Washington Post, which Trump criticizes for its coverage of his administration.

"We're getting tremendous complaints from other companies," Trump said in a press pool at the White House during a meeting with the prime minister of the Netherlands on Thursday. "Some of the greatest companies in the world are complaining about it."

In the letter, Thornberry and Reps. Elise Stefanik, R-N.Y.; Michael Turner, R-Ohio, and Robert Wittman, R-Va., said they've overseen the contract's handling "from the beginning."

"As you know, the courts have upheld DOD's handling of the competition," the letter said. "While it is understandable that some of the companies competing for the contract are disappointed at not being selected as one of the finalists, further unnecessary delays will only damage our security and increase the costs of the contract."

A White House spokesperson did not immediately respond to CNBC's request for comment.