New York, New York - Jury selection began on Monday in the trial of powerful US senator Robert Menendez charged with corruption after gold bars and hundreds of thousands of dollars in cash were found at his home.

Senator Robert Menendez, a 70-year-old Democrat from New Jersey, and his wife Nadine are accused of extortion, obstruction of justice, and accepting bribes to perform favors for businessmen with connections to Egypt and Qatar.

Menendez, the former chairman of the influential Senate Foreign Relations Committee, is on trial in a 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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Nadine Menendez is to be tried separately in July.

In the Egypt-related case, Menendez is accused of accepting bribes to use his "power and influence" to enrich his co-conspirators and "benefit the government of Egypt."

Menendez, who has rejected calls for his resignation, allegedly helped Hana protect his monopoly on US exports of halal food products to Egypt.

The senator is also accused of helping funnel US military assistance to the government in Cairo.

In the Qatar case, Menendez allegedly received bribes to assist Daibes, who was seeking millions of dollars in investment from a fund with ties to the oil-rich state.

In a raid on Menendez's New Jersey home, FBI agents allegedly found nearly $500,000 in cash hidden around the house.

Gold bars worth around $150,000 and a luxury Mercedes-Benz convertible, gifted by one of the businessmen, were also recovered.

A senator since 2006 and before that a member of the House of Representatives for 14 years, Menendez has been a Democratic stalwart in Congress for three decades.

Menendez, whose parents immigrated to the United States from Cuba, was indicted on bribery and corruption charges in 2015, but that case ended in a mistrial in 2017.

Menendez is up for reelection in November. A number of fellow Democrats, including New Jersey Governor Phil Murphy, have urged him to step aside, but Menendez has suggested that he might run as an independent.