US Secretary of State Mike Pompeo is accusing a senator of blocking President Donald Trump's nominees to key diplomatic posts, including ambassador to Kenya.
Kyle McCarter, a Trump ally and director of a Christian ministry in Kenya, was named nearly seven months ago as the proposed replacement for Mr Robert Godec, who has held the US envoy post since 2012.
Mr McCarter's appointment remains in limbo due to Democratic senators' objections to his political views, including his suggestion that Hillary Clinton should be imprisoned.
Democratic members of the Senate Foreign Relations Committee grilled Mr McCarter at a July 31 hearing on his nomination.
They criticised his opposition to same-sex marriage and Obama administration refugee policies, as well as his Twitter posting on the night of Mr Trump's 2016 election victory.
“Hillary for Prison. No, really,” Mr McCarter had tweeted in regard to the defeated Democratic presidential nominee.
Mr McCarter indirectly apologised for that posting after being rebuked at the hearing by Senator Tom Kaine, Mrs Clinton's running mate in 2016.
“How does a thought like that come into the brain of someone?” Senator Kaine asked Mr McCarter. “It seems so contrary to the values of a democratic society.”
Mr McCarter responded: “It is one of those tweets you’d like to reel in but can’t.”
Secretary of State Pompeo last week singled out Robert Menendez, the senior Democrat on the Senate Foreign Relations Committee, as chiefly to blame for delays in confirming Mr McCarter and dozens of other Trump nominees for positions in the State Department and in US embassies.
"These outstanding candidates remain unconfirmed because Senator Menendez and some of his colleagues are using our nominees as a political football," Mr Pompeo declared. "This is unacceptable."
Senator Menendez fired back, charging that "a slew of nominees have track records of deeply offensive public statements unbefitting of an official representative of the United States."
The Democratic senator from the state of New Jersey added that a State Department spokeswoman had erred in recently including Mr McCarter in a group of ambassadorial nominees who have held US Foreign Service posts.
"The nominee for Kenya is not a Foreign Service Officer, rather a political appointee who has publicly advocated for the imprisonment of Donald Trump’s political opponents," Senator Menendez said.
The Senate Foreign Relations Committee must clear a president's ambassadorial nominees before they face a required confirmation vote by the 100-member Senate.
Members of Mr Trump's Republican Party control both the committee and the full Senate, but congressional protocol gives minority-party members the ability to delay confirmations.