The top Republican and top Democrat from the Senate Homeland Security Committee on Wednesday implored President Trump to pick a nominee to lead the Department of Homeland Security and to fill the many other empty leadership positions at the sprawling government agency.

Sen. Ron Johnson (R-Wis.), the committee chairman, and Sen. Gary Peters (Mich.), the senior Democrat, sent Trump a letter urging him to “promptly” submit nominees for DHS secretary and “all vacant positions at the Department.”

“Currently, 7 of the 18 DHS offices requiring Senate confirmation, including the Department’s top three positions, are vacant with no nominee pending,” the senators wrote. “Many of these positions have remained vacant for months, and some for years, without a formal nominee for the Senate to consider.”

The letter was a sign of the bipartisan frustration with the president’s insouciant approach to the constitutional advice-and-consent process that gives senators a chance to question and vote on nominees for executive and judicial appointments.

They have been particularly dismayed by the hollow upper ranks at DHS, the third-largest federal agency, with 240,000 employees. The department’s centralized command structure, created after the 9/11 terrorist attacks, was meant to project stability at the top of the nation’s critical security agencies.

Trump has said repeatedly he prefers having top officials in an “acting” capacity because it makes it easier for him to fire them.

The senators, in their letter, categorically reject that approach.

“The widespread use of temporary leadership — individuals who, though perhaps qualified, do not serve with the imprimatur of having been confirmed by the Senate — makes it more difficult for the Department to achieve its long-term strategic objectives,” Johnson and Peters wrote, warning of the “dangers of pervasive vacancies to government accountability and national security.”

“The American people deserve leaders who will ensure stability and accountability to the Department,” they told Trump.

Kevin McAleenan, the current acting DHS secretary, has served in an interim role since April, when Trump removed the Senate-confirmed Kirstjen Nielsen from the job. Despite support for McAleenan among senators of both parties, he was never nominated to be the permanent secretary. He submitted his resignation on Oct. 11, with the goal of departing by the end of October.

The White House has struggled to find someone to fill the vacancy, and Trump’s preferred pick, Ken Cuccinelli, the acting director of U.S. Citizenship and Immigration Services, was determined to be ineligible for the job and has been panned by key GOP senators who dislike him. McAleenan has agreed to stay on temporarily to ensure a smooth transition to the next secretary.

The White House said last week that Trump will appoint Chad Wolf, Nielsen’s former chief of staff, as acting DHS secretary, but Wolf will not be the president’s choice for the permanent position. Further complicating the transition is Wolf’s pending confirmation as DHS undersecretary for strategy, plans and policy.

Senate Majority Leader Mitch McConnell (R-Ky.) is aiming to hold a confirmation vote for Wolf next week, according to congressional staffers. If confirmed for that job, he is expected to be promptly sworn in as acting DHS secretary, allowing McAleenan to depart.

The deputy secretary job at DHS remains vacant, as well as the department’s third-ranking position, the undersecretary for management. The heads of U.S. Customs and Border Protection, U.S. Immigration and Customs Enforcement, and the Federal Emergency Management Agency are also serving in acting roles.