By Saqib Iqbal Ahmed NEW YORK (Reuters) -The dollar edged higher against a basket of currencies on Tuesday, to scale a fresh two-decade high, as traders braced for an aggressive rate hike from the U.S. Federal Reserve this week to try to curb inflation. Rising expectations that the Fed will raise interest rates by more than previously forecast unsettled investors on Monday and sent the S&P 500 tumbling to confirm a bear market and intensifying fears over the economic outlook. There is a nearly 90% expectation for a 75 basis-point increase at the conclusion of a two-day Fed meeting on Wednesday…