U.S. stock index futures edged lower on Friday, pausing after the previous session's rally set Wall Street's main indexes on track for weekly gains following the Federal Reserve's pivotal stance on monetary policy earlier in the week.

U.S. stocks are drifting in early trading after leaping to records the day before as part of a worldwide rally.

"This would be the third time that stocks entered a cycle where annual returns compound at high teens," Fundstrat's Tom Lee said.