Story highlights Sen. Bob Corker was in the running to be secretary of state

The Tennessee Republican first joined the US Senate in 2007

(CNN) Tennessee Republican Sen. Bob Corker said Tuesday he will retire at the end of 2018.

"After much thought, consideration and family discussion over the past year, Elizabeth and I have decided that I will leave the United States Senate when my term expires at the end of 2018," Corker said in a released statement.

Corker is the Senate's foreign relations committee chairman and had told CNN earlier this month that he was considering whether to run agai n.

"When I ran for the Senate in 2006, I told people that I couldn't imagine serving for more than two terms," Corker said in his statement Tuesday. "Understandably, as we have gained influence, that decision has become more difficult. But I have always been drawn to the citizen legislator model, and while I realize it is not for everyone, I believe with the kind of service I provide, it is the right one for me."

Corker, who was at one time among those considered a candidate to be President Donald Trump's secretary of state, had been increasingly critical of the President in recent months.

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