MILWAUKEE (Reuters) - Republican presidential front-runner Donald Trump predicted that the United States is on course for a “very massive recession,” warning that a combination of high unemployment and an overvalued stock market had set the stage for another economic slump. “I think we’re sitting on an economic bubble. A financial bubble,” the billionaire businessman said in an interview with The Washington Post published on Saturday.  Coming off a tough week on the campaign trail in which he made a series of missteps, Trump’s latest comments bring him back into the limelight ahead of Tuesday’s important primary in Wisconsin where he trails in the polls. The former reality TV star said that the real U.S. jobless figure is much higher than five percent number released by the U.S. Bureau of Labor Statistics.  “We’re not at 5 percent unemployment,” Trump said. “We’re at a number that’s probably into the twenties if you look at the real number,” he said, adding that the official jobless figure is “statistically devised to make politicians — and in particular presidents — look good.”     Trump said “it’s a terrible time right now” to invest in the stock market, offering a more bleak view of the U.S. economy than that held by many mainstream economists. The interview was bylined by the Post’s Robert Costa and famed Watergate reporter Bob Woodward.  A real estate magnate, Trump has made appealing to blue-collar workers a hallmark of his bid for the Republican nomination for the Nov. 8 presidential election, often blaming unemployment on the outsourcing of U.S. jobs and facilities to countries such as China and Mexico. Trump vowed in the interview to wipe out the more than $19 trillion national debt “over a period of eight years,” helped by a renegotiation of trade deals. “I’m renegotiating all of our deals, the big trade deals that we’re doing so badly on,” he said. After making controversial statements about abortion last week, Trump has shown little sign of heeding calls from fellow Republicans to adopt a more presidential tone so as to avoid alienating voters in the November general election if he wins the nomination. On Saturday, he questioned close U. S. ties to Saudi Arabia and again accused U.S. allies of not pulling their weight in the NATO military alliance.  Trump told a campaign rally in Racine, Wisconsin that partners in the North Atlantic Treaty Organization “are not paying their fair share” and called the 28-nation alliance “obsolete.” “Either they pay up, including for past deficiencies, or they have to get out. And if it breaks up NATO, it breaks up NATO,” Trump said. Tuesday’s Wisconsin nominating contest could be a turning point in the Republican race. Trump, 69, trails his leading rival, U.S. Senator Ted Cruz, 45, of Texas in the state. A Cruz win would make it harder for Trump to reach the number of 1,237 delegates needed to secure the nomination before the Republican national convention in July. The winner will get to claim all of Wisconsin’s 42 delegates. 