Kaymer opens with birdie to lead US Open by four
Martin Kaymer of Germany lines up a putt on the tenth green during the second round of the 114th US Open on June 13, 2014 in Pinehurst, North Carolina - by Ross Kinnaird
The 29-year-old from Dusseldorf, who fired the lowest US Open round ever shot at Pinehurst with a five-under par 65 on Thursday, reached six-under as he began round two in cool and overcast conditions.
Kaymer, whose first major title came at the 2010 PGA Championship, is coming off a victory last month at the Players Championship.
Standing in second on two-under were three afternoon starters -- Americans Kevin Na and Fran Quinn and Northern Ireland's Graeme McDowell -- and Zimbabwe's Brendon de Jonge.
De Jonge fired a 68 Thursday and opened with a bogey on Friday but answered with a birdie at the third to keep himself on two-under for the tournament.
Dustin Johnson opened with a birdie at the 10th but dropped back to one-under with a bogey at 13 while fellow American Steve Stricker birdied the third hole to rise to one-under.