WASHINGTON (AFP) — Joe Biden's party won a new US Senate seat on Tuesday with Democrat Raphael Warnock's victory in Georgia, according to television networks.

The incumbent senator defeated Republican Herschel Walker, a former football star and protege of former president Donald Trump.

The victory confirms the very slim Democratic majority — 51 to 49 — in the upper house of Congress.

Warnock's victory does not change the balance of power in the Senate, which Democrats had already secured control of on 8 November.

But the victory allows Democrats to significantly curb the power of centrist Democratic senator Joe Manchin, who has already blocked several major Biden initiatives in the first two years of his term.

Warnock, 53, is a pastor and Walker, 60, is considered one of the best players in the history of American college football. Both African American faced voters after neither earned more than 50 percent in the 8 November midterm vote.

Historically a Republican state, Georgia took America by surprise when voters chose Biden over Trump in the 2020 presidential election and then sent two Democrats to the Senate two months later in another runoff.