Brooks Koepka admitted the final round of the US PGA Championship was "stressful" after a dramatic win on Sunday.

The American defended his title in New York despite a back-nine collapse at Bethpage Black, winning by two shots from Dustin Johnson.

But Koepka made his fourth major victory difficult, bogeying five of his final eight holes as his seven-stroke overnight lead was briefly cut to one.

He was happy to get the job done after shooting a four-over 74 in the final round, becoming the first man to win both the U.S. Open and US PGA titles back-to-back.

"I'm just glad we didn't have to play any more holes. That was a stressful round of golf," Koepka said at the trophy presentation.

"The wind was up, DJ played awesome, congrats to him, he put the pressure on but I'm glad to have this thing back in my hands."

Johnson's charge fell short after the 2016 U.S. Open champion bogeyed the 16th and 17th holes.

Koepka said he was aware of Johnson, who finished with a one-under 69 in the fourth round.

"How could you not with the DJ chants? I heard everything," he said.

"He did an unbelievable job putting pressure on me, making me play some solid golf coming down the end."