Secretary of State Antony Blinken wrote to senators on Monday urging them to confirm dozens of diplomatic nominees awaiting a vote, warning leaving various ambassadorships vacant could undermine U.S. national security.

Blinken in his letter noted that of the 38 State Department nominees awaiting a vote on the Senate floor, 35 of them are career officers. The note comes as Sen. Rand Paul (R-Ky.) has blocked votes on diplomatic nominees over a request for more information about the origins of COVID-19.

“Vacant posts have a long-term negative impact on U.S. national security, including our ability to reassure Allies and partners, and counter diplomatic efforts by our adversaries,” Blinken wrote.

“Not having a confirmed U.S. ambassador makes us less effective at advancing every single one of our policy priorities – priorities that are critical to our national security,” he added, citing efforts to get other countries to act as Special Immigrant Visa processing hubs and outreach to building coalitions to fight drug trafficking as examples.

Without Senate action, Blinken wrote, posts in Egypt, Israel, Jordan and Lebanon will have no confirmed ambassadors this summer as outgoing officials retire or cycle out.

Blinken also warned of the potential long-term ripple effects of holding up nominees for reasons unrelated to their qualifications.

“If the new standard is that career State nominees are subject to holds unrelated to the merits of their nominations, and must be individually confirmed by floor vote, then our leadership and standing in the world will suffer, with dozens of continuous vacancies that will take years to resolve, if ever,” Blinken wrote. “Our diplomatic strength will be weakened and competitors will gain at our expense.”

Paul announced earlier this year that he would block State Department nominees up for a vote in the Senate until the administration released additional documents outlining the source of the coronavirus.

A State Department spokesperson said Monday that the administration cannot provide the documents Paul is requesting because “they are not in our possession.”

The hold on State Department nominees comes amid frustration among Democrats and within the Biden administration over GOP Sen. Tommy Tuberville’s (Ala.) separate hold on Pentagon nominees in protest of the Defense Department abortion policy.