WASHINGTON—Alan Greenspan says the country can’t afford tax cuts of the magnitude proposed by Republican presidential contender John McCain — at least not without a corresponding reduction in government spending. “Unless we cut spending, no,” the former Federal Reserve chairman said Friday when asked about McCain’s proposed tax cuts, pegged in some estimates at $3.3 trillion. “I’m not in favor of financing tax cuts with borrowed money,” Greenspan said during an interview with Bloomberg Television. “I always have tied tax cuts to spending.” McCain has said that he would offset his proposed cuts—including reducing the corporate tax rate and eliminating the Alternative Minimum Tax that has plagued middle-class families.