(Reuters) - Warren Buffett is closely monitoring whether U.S. President Donald Trump can lower corporate taxes, one of the rare times the billionaire has looked to Washington to help him decide which stocks to buy and sell. “It’s an actual factor at Berkshire,” Buffett, the chairman of Berkshire Hathaway Inc (BRKa.N), said in a Tuesday interview with CNBC television. “And it’s very, very, very seldom in my 87 years that it has ever been a factor.” Buffett normally buys stocks for the long term with less focus on tax issues. But when asked if he was thinking about taxes, he said “I think about them plenty” now. “We’ve got actions on both sides that we would take,” referring to taking gains or realizing losses, he said. Berkshire has said it ended June with more than $135 billion of equity investments, which Buffett mainly controls and holds for the long term. The conglomerate is sitting on huge gains in big investments such as American Express Co (AXP.N), Coca-Cola Co (KO.N) and Wells Fargo & Co (WFC.N), while other bets such as International Business Machines Corp (IBM.N) have fared less well. Buffett had said at Berkshire’s annual meeting in Omaha, Nebraska, on May 6 that he would rather realize losses than take gains if he expected rates to fall. That might be a good strategy now, if Trump and many congressional Republicans succeeded in lowering the top corporate tax rate to 20 percent from 35 percent. Buffett explained that he would “feel kind of silly” realizing a $1 billion gain and paying $350 million in taxes, only to have Congress lower the rate and thus his tax bill. He said other investors sitting on “hundreds of billions” of dollars of potential profits might be thinking the same thing. It is unclear whether the Republican-controlled Congress can pass a tax bill that Trump will sign, and Buffett said it has been unable to overhaul the Affordable Care Act or move forward on infrastructure, two of the president’s priorities. He expects to know by year end whether taxes are going down. “I would think the Republicans controlling both houses [of Congress] and the presidency, they would not want to have a shutout, in their first year,” Buffett said. “I think they can get it done.” 