Donald Trump's pick for defence secretary has pledged to carry on and said he still has the president-elect's backing amid reports he could be replaced.
Mr Trump was said to be considering ditching Pete Hegseth in favour of Florida governor Ron DeSantis.
There are doubts Mr Hegseth could clear the Senate vote required due to claims about his personal and professional life.
On Wednesday, he met Republican senators whose vote he will need to be confirmed, and in a clip posted on X told a CBS News reporter he still had Mr Trump's backing.
He said: "I spoke to the president-elect this morning. He said 'keep going, keep fighting'... Why would I back down? I've always been a fighter. I'm here for the warfighters. This is personal and passionate for me."
Mr Trump's picks for his cabinet have attracted controversy and there has been speculation some might struggle to be confirmed.
Matt Gaetz, his initial pick for attorney general, has already withdrawn from the process.
Two sources familiar with the decision-making told Sky News' US partner network NBC News that DeSantis, once a rival in the Republican presidential race, could be chosen to replace Mr Hegseth.
Mr DeSantis is "very much in contention", according to one source.
NBC News reported Mr Hegseth's nomination was in jeopardy after at least six Republican senators were wavering in their support.
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Mr Hegseth, a former Fox News host, has attracted controversy over claims of excessive drinking, financial mismanagement and treatment of women.
An article in the New Yorker magazine reported that the allegations led to him having to quit leadership roles in two separate non-profit organisations for military veterans.
Mr DeSantis pulled out of the contest to be the Republican nominee for president in January after falling well behind Mr Trump in the primary campaign.
(c) Sky News 2024: Trump's defence pick Pete Hegseth 'won't back down' amid claims he could be replaced by Ron DeSantis