NEW YORK (Reuters) - Grand slam king Roger Federer came back with renewed vigor after a weather delay to rout Spaniard Marcel Granollers 4-6 6-1 6-1 6-1 and charge into the fourth round of the U.S. Open on Sunday.

The 42nd-ranked Granollers surprisingly led the second-seeded Swiss 5-2 when lightning and heavy rains suspended their afternoon match at Arthur Ashe Stadium.

After play resumed a couple of hours later, 17-times grand slam winner Federer conceded the first set and trailed 1-0 in the second before reeling off nine straight games and a total of 18 of the next 20 to register the one-sided victory.

"I was able to come back and turn it around, because Marcel started really on fire," 33-year-old Federer told the crowd. "I'm happy the break helped me and I came out and played some great tennis."

Five-times U.S. Open winner Federer will next play either 17th seed Roberto Bautista Agut of Spain or France's Adrian Mannarino.

(Reporting by Larry Fine; Editing by Ian Ransom)