Mitt Romney, former Republican White House hopeful and outspoken critic of President Donald Trump, announced on Friday that he is seeking a US Senate seat in Utah, beginning a closely-watched return to the national political stage.

“I am running for United States Senate to serve the people of Utah and bring Utah's values to Washington,” Romney wrote on Twitter.

Romney, who also posted a video clip making the announcement, is running for a seat currently held by Republican Orrin Hatch, who in early January announced his retirement against the urgings of Trump.

“Utah welcomes legal immigrants from around the world. Washington sends immigrants a message of exclusion. And on Utah Capitol Hill, people treat each other with respect,” Romney says on the video, in an apparent jab at the Trump administration's policy on migrants.

A wealthy businessman and former governor of Massachusetts, Romney was the 2012 Republican presidential nominee.

His strong name recognition and stature as a respected establishment Republican would make him the instant frontrunner in conservative Utah, where he also has roots.

In a 2016 speech, Romney called fellow Republican Trump a “phony, a fraud,” who was "playing the members of the American public for suckers."