Trenton, New Jersey - Democratic Senator Robert Menendez, who is on trial for corruption in office, has registered to run for reelection as an Independent, according to documents filed Monday, threatening President Joe Biden's control of the Senate.

The move comes as Menendez refuses to step down and Democrats run a separate candidate in November's race – a matchup that could split voters and lead to a Republican winning the seat in New Jersey, a Democratic stronghold.

Menendez, charged with extortion, obstruction of justice, and accepting bribes to perform favors for businessmen with connections to Egypt and Qatar, registered to run under the "Menendez for Senate" party banner.

The 70-year-old secured 2,465 signatures from members of the public for his Independent run, more than the 800 required, the state's candidate list showed.

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Biden, himself up for reelection in November, is vying to cling to a razor-thin 51-49 Senate majority, with 10 Republican and 23 Democratic seats up for grabs – including Menendez's in New Jersey.

Menendez, who remains in office, led the influential Senate Foreign Relations Committee until the charges were filed in September.

He is on trial in federal court in Manhattan with two of the businessmen – Egyptian-American Wael Hana and Fred Daibes, a real estate developer.

A third businessman, insurance broker Jose Uribe, pleaded guilty to bribery charges in March and has been assisting investigators.

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The senator's wife Nadine Menendez (57) is to be tried separately in July.

The most serious charges could carry up to 20 years in prison upon conviction.

A senator since 2006 and before that a member of the House of Representatives for 14 years, Menendez, whose parents emigrated to the US from Cuba, has been a Democratic stalwart in Congress for three decades.

Andy Kim, who will contest the seat for Biden's Democrats, wrote on X that "everyone knows Bob Menendez isn't running for (New Jersey) families. He's running for himself."