Two efforts to negotiate a plea deal this year for the Chinese billionaire accused in a United Nations bribery scheme were unsuccessful, a federal prosecutor told the judge Monday as jury selection in the trial of Ng Lap Seng began in federal court in Manhattan.

Ng, 69, a real estate and casino magnate from Macau, is charged with paying more than $500,000 in bribes to UN ambassadors and officials to get support for a conference center he wanted to develop in Macau.

Prosecutor Janis Echenberg told U.S. District Judge Vernon Broderick that plea offers in May were made and rejected, and then renewed this month, again unsuccessfully.

Ng was arrested in late 2015 after making several visits to the United States with large cash sums that he said were for gambling, purchases of art, and renovations to an Old Brookville house owned by a man whom the government suspected of being a Chinese intelligence agent.

He eventually was charged with paying off John Ashe, a diplomat from Antigua who served as UN General Assembly president, and Francis Lorenzo, a Dominican diplomat. Ashe died after he was charged, and Lorenzo is expected to be a key government witness.

The defense, in court filings, has said the United States is using a criminal case against Ng as a pretext to try to limit growing Chinese influence among less-developed countries that would have been served by the planned conference center.

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The government, in court filings, has suggested that Ng, who has a political role as a member of the People’s Political Consultative Conference, was acting at the behest of the Chinese government.

Ng was previously embroiled in a U.S. fundraising scandal through his links to Charlie Trie, a Chinese businessman who tried to funnel money to support Bill Clinton in the 1990s. But Broderick has ruled testimony about that episode off-limits.

As jury selection began on Monday, Broderick told a pool of 138 prospective jurors that the trial is expected to last 4 to 6 weeks. Opening statements are expected on Tuesday.