Washington (CNN) As President Donald Trump's pick for secretary of state, Mike Pompeo, prepares to face lawmakers for his second major confirmation hearing as a Trump nominee, scores of former diplomats are urging lawmakers to "focus public attention on the urgent need to restore the power and influence of American diplomacy."

In an open letter to Sens. Bob Corker and Robert Menendez -- the top Republican and Democrat on the Senate Foreign Relations Committee, respectively -- over 200 retired US diplomats pleaded for a congressional effort to ensure the State Department has the personnel and resources it needs to carry out its mission.

"Our great country faces challenges both today and in the future which require that we have a diplomatic force ready to keep America safe in partnership with the brave men and women of our armed forces," the authors wrote.

Among the letter's signatories are senior diplomats who've served under Republican and Democratic presidents in posts around the world. The majority were career officials, and all served as either ambassadors, assistant secretaries of state, or under secretaries of state. One of the authors, Amb. Bill Burns, attained the rank of deputy secretary of state during the Obama administration.

The letter was posted online by the non-partisan advocacy group Foreign Policy for America, which recently launched a "#DefendDiplomacy" campaign to draw attention to widespread vacancies in the State Department's upper ranks.

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