WASHINGTON, United States (AFP) — Republican Kelly Loeffler on Thursday conceded her closely watched Senate race in Georgia, with Democratic wins in the state's two runoff elections sealing the party's control of the chamber later this month.

"Earlier today I called Reverend Warnock to congratulate him and to wish him well in serving this great state," the businesswoman said in a video message.

It was a clear change in tone from her campaign, during which she blasted Raphael Warnock, the pastor of Martin Luther King's Atlanta church, as a "radical liberal" who threatened American values.

Loeffler, who will serve out the remainder of her term, had planned to object in Congress on Wednesday to the certification of President-elect Joe Biden's November 3 victory.

But after the violence that day at the Capitol, which was overrun by mobs of supporters of President Donald Trump, the senator changed her mind, saying she could not oppose certification "in good conscience".

She had campaigned Monday night alongside Trump at a large rally in Dalton, Georgia. 

Democrats pulled off upsets in the dual Senate run-off elections on Tuesday.

Warnock will become the first Black senator from Georgia, and Jon Ossoff, the other successful candidate, will be the southern state's first Jewish senator.

Ossoff will also be the youngest Democratic senator since Biden himself joined the chamber in 1973 at age 30.

They will take office once their victories are certified in Georgia, which authorities have to do by January 22.

Republicans will retain control of the Senate until January 20, when President-elect Biden and his vice president Kamala Harris are inaugurated.

When the two new senators take office, Democrats will have 50 seats in the Senate, same as the Republicans.

As vice president, Harris will cast tiebreaking votes in the Senate, if needed — giving Democrats control of the chamber.

Until Trump leaves the White House, it is Vice President Mike Pence who will hold the tiebreaking vote.