WASHINGTON - US Republican presidential candidate Donald Trump said on Monday he supported the use of US ground troops to fight Islamic State in the Middle East.Speaking on MSNBC's "Morning Joe" program, the billionaire businessman said it would take American soldiers to target the militant group."They have great money because they have oil," Trump said. "Every place where they have oil I would knock the hell out of them.""I would knock out the source of their wealth, the primary sources of their wealth, which is oil. And in order to do that, you would have to put boots on the ground. I would knock the hell out of them but I'd put a ring around it and I'd take the oil for our country," he told MSNBC.In addition to cutting off Islamic State's oil income, Trump said the militants' money in the banking system would also have to be targeted, although he did not offer any details."You have to cut that off," he said.Trump's comments follow last's week's first prime-time televised debate for Republican presidential candidates. The real estate mogul and television personality leads public opinion polls, putting him at the top of the 17-person pack of Republicans heading into the 2016 election for the White House.