TOKYO, Jan 28 (Reuters) - The dollar gained to a six-month high against the euro and hit a near five-month peak versus a basket of currencies on Thursday boosted by speculation over higher interest rates in the United States.

The euro slipped as low as $1.3990 on trading platform EBS, the lowest since mid-July, before trading at $1.4003, down 0.1 percent on the day.

The dollar index, a gauge for the greenback's performance against other six major currencies rose as far as 78.867 .DXY, the highest since early September.