Oct 28 (Reuters) - Alex Saab, a Colombian businessman who became a special envoy for Venezuelan President Nicolas Maduro, will plead not guilty to money laundering charges when arraigned on Monday, his lawyer Henry Bell told Reuters. In a case that pits the United States against Maduro"s socialist administration, Saab was arrested last year in Cape Verde during a refueling stop en route to Iran and extradited to the United States earlier this month. He and an ally have been charged with siphoning around $350 million out of Venezuela via the United States as part of a bribery scheme linked to Venezuela"s state-controlled exchange rate. "Of course our client will be pleading not guilty when arraigned," Bell told Reuters. When sanctioning him in 2019, Washington described Saab as an orchestrator of a "vast corruption network" that enriched Maduro and his allies through a complex web of shell companies, business associates and relatives. Lawyers for Saab, 49, have called the U.S. charges "politically motivated" and his family says Saab has been "kidnapped" by the United States. Washington labels Maduro an illegitimate dictator and has sanctioned the OPEC nation"s state oil company in a bid to pressure him to step down, while several top Venezuelan officials - including Maduro himself - face U.S. drug trafficking charges. Venezuela"s opposition is hoping Saab cooperates with investigators and sheds light on what they say has been widespread graft in the oil-rich nation. To be sure, an initial not guilty plea does not preclude negotiations over a possible plea deal, and defendants in U.S. criminal cases may change their pleas before a case goes to trial. "It is routine for defendants to enter a plea of not guilty at their arraignment," said Stef Cassella, a former federal prosecutor. "That does not foreclose the possibility that the defendant will later change his plea to guilty as part of a cooperation agreement with the government." FROM CONSTRUCTION TO DIPLOMACY The United States says Saab repeatedly bribed Venezuelan officials, as well as Maduro"s three stepsons, in exchange for access to lucrative contracts. Saab, who worked in Venezuela for more than a decade, has reportedly had business dealings in an array of industries including oil, food, currency, medicine imports and construction. The Treasury Department says Saab bribed Maduro"s relatives to win no-bid, overvalued contracts to import food for a government-run handout program as hunger surged in Venezuela amid an economic crisis. They also say an early government construction contract paid Saab and a business partner three to four times the actual cost of building the homes. Court records show that Venezuela"s foreign ministry named Saab a special envoy in April 2018, and tasked him with a mission to seek aid from Iran in 2020. "When things got tough, Mr. Alex Saab was one of the few who said he was willing," Socialist Party Vice President Diosdado Cabello said earlier this month. "He was one of the people assigned to mock imperialism"s persecution of our nation. He was able to get even gas, medicine and food into Venezuela. Of course he was paid!"