WASHINGTON — The Trump administration's intelligence watchdog has declined a request from four top Senate Democrats to investigate how the White House has handled security clearances for Jared Kushner, Ivanka Trump and other employees, according to a letter obtained by NBC News.

Michael Atkinson, the inspector general of the intelligence community, meaning the chief internal watchdog for the nation's intelligence agencies, wrote to the senators that he would be happy to conduct such an investigation, but could only do it if President Donald Trump asks him.

"The authority over access to classified information ultimately rests with the President of the United States," Atkinson wrote to Sen. Mark Warner of Virginia, the ranking Democrat on the Intelligence Committee, and the three other senators. "It is well-established that the President of the United States has broad latitude concerning the process through which security clearances are granted, transferred, or revoked, as well as broad flexibility in determining whom to choose as his advisors and to what extent those advisors may gain access to information, including national security information."

"Given the concerns raised by your letter, the ICIG is available and willing to conduct a review, similar to that suggested in your letter, at the request of the President or his designees," he added.

Click here to read Atkinson's letter.

In response, the senators — Warner, Dianne Feinstein of California, ranking member on the Judiciary Committee; Bob Menendez of New Jersey, ranking member on the Foreign Relations Committee; and Jack Reed of Rhoda Island, ranking member on Armed Services — wrote a letter to Trump on Wednesday asking him to order an investigation.

"Over the last two years, public reporting has raised serious concerns about irregularities and questionable decisions related to eligibility determinations for (White House) personnel access to classified information," the letter said.

Click here to read the senators' letter to Trump.

The White House did not immediately respond to a request for comment. The White House has previously declined to comment on the security clearances.

The senator's Wednesday letter to Trump points to reports that individuals have been granted temporary access to extremely sensitive intelligence without undergoing a complete background investigation, and that the White House has extended these temporary clearances beyond the usual six-month time frame.

The letter also alludes to NBC News reporting that officials in the White House security office overruled unfavorable adjudication recommendations by career security professionals in more than 30 cases, including that of Kushner and Ivanka Trump, and that officials in the Executive Office of the President have threatened to revoke former officials' eligibility for access to classified information for reasons other than the adjudicative guidelines.

NBC News reported in January that Kushner's application for a top-secret clearance was rejected by two career White House security specialists after an FBI background check raised concerns about potential foreign influence on him — but their supervisor overruled the recommendation and approved the clearance, according to two sources familiar with the matter. NBC News later reported that career officials were also overruled when they balked at giving Ivanka Trump a top-secret clearance.

Kushner's was one of at least 30 cases in which a supervisor overruled career security experts and approved a top-secret clearance for incoming Trump officials despite unfavorable information, the two sources said. They said the number of rejections that were overruled was unprecedented.

The New York Times reported in February that President Trump ordered his chief of staff to grant Kushner a top-secret security clearance.