American investment guru Jim Rogers has signalled his lack of faith in the strength of the US dollar, conceding that he holds fewer greenbacks than he did a year ago.Speaking to Bloomberg, the author took particular issue with the public debt ratio in the States and said that he found it "mind-boggling" that anyone would offer long-term loans to the country at rates of less than six per cent.He went on to state: "The government is printing lots of money and borrowing even more; that's not the basis for a sound currency."Rogers, who has previously told the news agency that he intends to shift all his assets out of the dollar by the end of the year, added that he plans to take a short position on US bonds at some point in the near future.In the UK, short selling was temporarily restricted in the wake of the financial crisis amid fears that the practice was putting undue pressure on companies deemed to be at risk of falling into difficulty.