Washington - President Donald Trump's former campaign chair, Paul Manafort, secretly worked for a Russian billionaire to advance the interests of Russian President Vladimir Putin a decade ago and proposed an ambitious political strategy to undermine anti-Russian opposition across former Soviet republics, AP reports.The work appears to contradict assertions by the Trump administration and Manafort himself that he never worked for Russian interests.Manafort proposed in a confidential strategy plan as early as June 2005 that he would influence politics, business dealings and news coverage inside the United States, Europe and the former Soviet republics to benefit the Putin government, even as US-Russia relations under Republican President George W Bush grew worse. Manafort pitched the plans to Russian aluminium magnate Oleg Deripaska, a close Putin ally with whom Manafort eventually signed a $10m annual contract beginning in 2006, according to interviews with several people familiar with payments to Manafort and business records obtained by AP. Manafort and Deripaska maintained a business relationship until at least 2009, according to one person familiar with the work.Contract unclear"We are now of the belief that this model can greatly benefit the Putin government if employed at the correct levels with the appropriate commitment to success," Manafort wrote in the 2005 memo to Deripaska. The effort, Manafort wrote, "will be offering a great service that can re-focus, both internally and externally, the policies of the Putin government".Manafort's plans were laid out in documents that included strategy memoranda and records showing international wire transfers for millions of dollars. How much work Manafort performed under the contract was unclear.The disclosure comes as Trump campaign advisers are the subject of an FBI probe and two congressional investigations. Investigators are reviewing whether the Trump campaign and its associates co-ordinated with Moscow to meddle in the 2016 campaign. Manafort has dismissed the investigations as politically motivated and misguided and said he never worked for Russian interests. The documents obtained by AP show Manafort's ties to Russia were closer than previously revealed.Manafort confirmed in a statement that he worked for Deripaska in various countries but said the work was being unfairly cast as "inappropriate or nefarious" as part of a "smear campaign."I worked with Oleg Deripaska almost a decade ago representing him on business and personal matters in countries where he had investments," Manafort said. "My work for Mr Deripaska did not involve representing Russian political interests".Deripaska became one of Russia's wealthiest men under Putin, buying assets abroad in ways widely perceived to benefit the Kremlin's interests. US diplomatic cables from 2006 described Deripaska as "among the 2-3 oligarchs Putin turns to on a regular basis" and "a more-or-less permanent fixture on Putin's trips abroad." In response to questions about Manafort's consulting firm, a spokesperson for Deripaska in 2008 - at least three years after they began working together - said Deripaska had never hired the firm. Manafort worked as Trump's unpaid campaign chair last year from March until August. Trump asked Manafort to resign after AP revealed that Manafort had orchestrated a covert Washington lobbying operation until 2014 on behalf of Ukraine's ruling pro-Russian political party .Political interestsThe newly obtained business records link Manafort more directly to Putin's interests in the region. According to those records and people with direct knowledge of Manafort's work for Deripaska, Manafort made plans to open an office in Moscow and at least some of Manafort's work in Ukraine was directed by Deripaska, not local political interests there. The Moscow office never opened.White House spokesperson Sean Spicer said on Monday that Manafort "played a very limited role for a very limited amount of time" in the campaign, even though as Trump's presidential campaign chair he led it during the crucial run-up to the Republican National Convention.Manafort and his associates remain in Trump's orbit. Manafort told a colleague this year that he continues to speak to Trump by telephone. Manafort's former business partner in eastern Europe, Rick Gates, has been seen inside the White House on a number of occasions. Gates has since helped plan Trump's inauguration and now runs a non-profit organisation, America First Policies, to back the White House agenda.