WASHINGTON - US President Donald Trump complained on Wednesday that Russia was helping North Korea to evade international sanctions, signaling frustration with a country he had hoped to forge friendly relations with after his 2016 election win."Russia is not helping us at all with North Korea," Trump said during an Oval Office interview with Reuters. "What China is helping us with, Russia is denting. In other words, Russia is making up for some of what China is doing." China and Russia both signed onto the latest rounds of United Nations Security Council sanctions against North Korea imposed last year. There was no immediate comment from the Russian embassy in Washington on Trump's remarks.During a 53-minute interview with a fresh Diet Coke near at hand on his desk, Trump also said he was considering a big "fine" as part of an investigation into China's alleged theft of intellectual property; that he has lost all trust in the chief Democratic Party negotiator on immigration in the Senate; and declined to clear up conflicting reports about his use of the phrase "sh*thole countries" in a White House meeting, which caused an international outcry.With North Korea persisting as the major global challenge facing Trump this year, the president cast doubt on whether talks with North Korean leader Kim Jong Un would be useful. In the past he has not ruled out direct talks with Kim."I'd sit down, but I'm not sure that sitting down will solve the problem," he said, noting that past negotiations with the North Koreans by his predecessors had failed to rein in North Korea's nuclear and missile programs.He blamed his three immediate predecessors, Bill Clinton, George W. Bush and Barack Obama, for failing to resolve the crisis and, a day after his doctor gave him a perfect score on a cognitive test, suggested he had the mental acuity to solve it."I guess they all realized they're going to have to leave it to a president that scored the highest on tests," he joked.He declined to comment when asked whether he had engaged in any communications at all with Kim, with whom he has exchanged public insults and threats, heightening tensions in the region.Trump said he hoped the standoff with Pyongyang could be resolved "in a peaceful way, but it’s very possible that it can’t." Asked whether he thought the United States needs more missile defense systems, he said, "Yes, yes I do. We're ordering more missile defense and we're ordering more missile offense also." Trump praised China for its efforts to restrict oil and coal supplies to North Korea but said Beijing could do much more to help constrain Pyongyang.The White House last week welcomed news that imports to China from North Korea, which counts on Beijing as its main economic partner, plunged in December to their lowest in dollar terms since at least the start of 2014.