FILE - In this Thursday, June 27, 2019, file photo, Secretary of State Mike Pompeo, left, talks with U.S. Ambassador to Japan Bill Hagerty as Pompeo arrives in Osaka, Japan. In a tweet on Friday, July 12, 2019, President Donald Trump said Hagerty is running for Tennessee’s open U.S. Senate seat. (Jacquelyn Martin, Pool, File/Associated Press)

NASHVILLE, Tenn. — President Donald Trump on Friday announced in a tweet that U.S. Ambassador to Japan Bill Hagerty would launch a bid for Tennessee’s open U.S. Senate seat, giving the top Republican contender an unconventional entry into the state’s most competitive 2020 contest.

“Tennessee loving Bill Hagerty, who was my Tennessee (Victory) Chair and is now the very outstanding Ambassador to Japan, will be running for the U.S. Senate,” tweeted Trump, who won Tennessee by wide margins in 2016 and remains popular there. The president immediately said he was throwing his endorsement behind Hagerty’s bid.

Hagerty, 59, did not immediately respond to a request to confirm Trump’s announcement. Hagerty will have to step down from his diplomatic post to run for the office and is expected to do so soon.

The news comes a day after former Tennessee Gov. Bill Haslam confirmed he wouldn’t run for the position being vacated by outgoing Republican Sen. Lamar Alexander. That same day, Tennessee GOP U.S. Rep. Mark Green — also seen as a top candidate for the position — announced he wouldn’t run for Senate despite previously expressing interest.

Speculation over whether Haslam would enter the race had been a closely watched issue among Tennessee’s political circles. Haslam pushed off the decision for months after previously promising to make an announcement soon after leaving the governor’s mansion.

Since Hagerty once served as Haslam’s economic development commissioner, he was seen as unlikely to run against his old boss.

Hagerty has served in a number of executive positions ranging from chief financial officer, to chairman and chief executive officer. He also founded his own private equity and investment firm.

A longtime friend and adviser to former presidential candidate U.S. Sen. Mitt Romney, Hagerty also worked on the White House domestic policy staff during the George H.W. Bush administration as a member of the President’s Council on Competitiveness.

Trump nominated Hagerty as ambassador to Japan in early 2017, where he drew strong praise from Alexander, who called him “one of President Trump’s best appointments,” on the Senate floor during Hagerty’s confirmation. Alexander particularly touted Hagerty’s ability to speak Japanese.

Hagerty is expected to have prominent campaign strategist Ward Baker on his team. Baker helped lead Republican U.S. Sen. Marsha Blackburn to an 11-point win last year over popular former Democratic Gov. Phil Bredesen in an open Senate contest. Trump visited Tennessee multiple times to boost Blackburn’s candidacy.

Trauma surgeon Manny Sethi, who has Gov. Bill Lee’s former campaign manager Chris Devaney on his side, announced his entrance into the race last month.

“I deeply respect President Trump and am not at all surprised he’s with his own ambassador,” Sethi tweeted. “But I believe Tennesseans want a conservative outsider and they will have a clear choice in this campaign. Looking forward to it!”

Other Republicans are expected to join, including possibly U.S. Rep. David Kustoff who said Thursday he’s been approached by multiple people to run.

On the Democratic side, Nashville attorney and former Army helicopter pilot James Mackler has announced his candidacy. Mackler dropped out of the 2018 race when Bredesen opted to run for the seat vacated by former GOP Sen. Bob Corker.

Bredesen’s loss has been seen as a strong blow to Democrats who thought they had their best shot at a statewide elected office in years.

Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.