ISTANBUL

US Secretary of State Marco Rubio took the stand Tuesday in the federal trial of former Florida congressman David Rivera, who is accused of acting as an unregistered foreign agent for the Venezuelan government under Nicolas Maduro, and conspiracy to commit money laundering.

The testimony made Rubio the first sitting Cabinet member to testify in a criminal case since 1983.

Rivera, a longtime friend and former roommate of Rubio, and political consultant Esther Nuhfer, are accused of agreeing to a $50 million contract to secretly lobby the first Trump administration to soften its stance on Maduro's government. Rubio faces no charges in the case.

Rubio acknowledged his friendship with Rivera before the court, but said he had no involvement in or knowledge of Rivera's alleged scheme. He described a July 2017 meeting Rivera arranged to present a plan for transitioning Venezuela's leadership, saying he would not have taken subsequent action had he known Rivera was representing the interests of the Venezuelan government. "It most certainly would have influenced my decision to meet with him," Rubio said, according to the Washington Post.

When a second meeting Rivera set up with a Venezuelan telecommunications magnate, Rubio became increasingly frustrated. "It was more of the same. I was frankly angry and frustrated," he testified. "Why would I waste my time with a stupid meeting?"

Federal prosecutors alleged Rivera and Nuhfer also sought to influence Rubio and former White House adviser Kellyanne Conway on Maduro's behalf.