LONDON—The U.S. dollar index strengthened to 100 for the first time in nearly two years on Friday, supported by the prospect of a more aggressive pace of Federal Reserve interest rate hikes. The greenback has gained ground on a basket of rivals over the past month, particularly against the euro, which has been pressured by investor concerns about the economic costs of war in Ukraine. The dollar index rose as high as 100 in early European trading hours, its best level since May 2020. It later lost some momentum and was last broadly flat at 99.844. The index is up 1.3 percent this week, which would be its biggest increase in a month, backed by hawkish remarks from several Federal Reserve policy makers who are calling for a faster pace of interest rate increases to curb rapid inflation. This week’s release of the minutes of the Fed’s March meeting showed …