The defending champion began the day with a one-shot advantage over New Zealand’s Danny Lee, having produced a course record on the opening day at Bethpage State Park.

The chasing pack were even further adrift, with England’s Tommy Fleetwood third at four shots back.

Koepka drove further clear on the second day as the American carded a five-under round of 65.

That effort saw Koepka achieved the lowest 36-hole score in major championship history.

He now leads on 12 under par.

Fellow American Jordan Spieth and Australia’s Adam Scott are the closest challengers to Koepka, who is seeking a fourth major.

The duo are seven shots off the pace at five under par.

United States’ Dustin Johnson and England’s Matt Wallace are among four players a further shot down.

Tiger Woods headlined the list of players to miss the cut after the second round.

The Masters champion struggled to five over par over the two days.