Sunday's tee-off times: Dustin Johnson and Jason Day in final group

Big-hitting American Johnson used his power off the tee and a deft touch around the greens to rack up five birdies, along with three bogeys and a double at the par-four 13th, to card a level-par 70 in difficult scoring conditions at Chambers Bay.

South African Grace, a six-times winner on the European Tour whose game has long been praised by his compatriot Ernie Els, offset three birdies with three bogeys for a matching 70 to join Johnson, Jordan Spieth and Jason Day at four-under 206. "I actually played some great golf and the concentration slipped a little bit around the turn," Grace told reporters. "I'm still happy. I'm still in a good position, I'm grinding away. It was a good day out there, but it was tough.

"Tomorrow is just going to be another tough grind. The course really firmed up towards the end and played really bouncy and tricky." Johnson, like Grace bidding for his first major title, was also happy with his form on a challenging afternoon on a firming course.

"I played really well today," said the 30-year-old American. "Obviously the setup was very difficult, the golf course is playing really firm and fast. It's just tough out there.

"A few three-putts, other than that, I felt like I putted it well. I just missed a few short ones. I made some putts, too. But really could have been a good day today."

Johnson, a nine-times winner on the PGA Tour, is well aware of the challenge facing him in the final round of a major on a difficult layout where danger lurks at every corner. In the 2010 U.S. Open at Pebble Beach, the American squandered a three-shot lead on the last day, slumping to an 82.

That same year in the PGA Championship at Whistling Straits, he was slapped a two-stroke penalty for grounding his club in a waste bunker on the 18th hole to miss out on a playoff for the trophy.

"I've been in the situation a few times so I know how to handle myself," said Johnson. "I know what it takes to get it done ... just need to go out there and focus one shot at a time. And we'll see what happens."

15:55: Camilo Villegas (Col)

16:06: Ben Martin; Chris Kirk

16:17: Zach Johnson; D.A. Points

16:28: Andy Pope; Nick Hardy (a)

16:39: Phil Mickelson; Brad Elder

16:50: Sam Saunders; Lee Westwood (Eng)

17:01: Marcus Fraser (Aus); Pan Cheng-tsung (Tai)

17:12: Angel Cabrera (Arg); Morgan Hoffmann

17:23: Ernie Els (SA); Mark Silvers

17:34: Thomas Aiken (SA); Brian Campbell (a)

17:45: Cameron Tringale; Luke Donald (Eng)

17:56: Ryan Palmer; Billy Horschel

18:07: Robert Streb; Kevin Chappell

18:18: Jim Furyk; George Coetzee (SA)

18:29: Jimmy Walker; Troy Kelly

18:40: Colin Montgomerie (Sco); Geoff Ogilvy (Aus)

18:51: Beau Hossler (a), Tommy Fleetwood (Eng)

19:02: Brad Fritsch (Can); Keegan Bradley

19:13: John Parry (Eng); Webb Simpson

19:24: Daniel Summerhays; Denny McCarthy (a)

19:36: Jimmy Gunn (Sco); Sergio Garcia (Spa)

19:48: Paul Casey (Eng); Jack Maguire (a)

20:00: Ollie Schniederjans (a); Justin Rose (Eng)

20:12: Kevin Na; Marc Warren (Sco)

20:24: John Senden (Aus); Rory McIlroy (NI)

20:36: Brooks Koepka; Ian Poulter (Eng)

20:48: Jamie Lovemark; Jason Dufner

21:00: Hideki Matsuyama (Jap); Adam Scott (Aus)

21:12: Francesco Molinari (Ita); Charlie Beljan

21:24: Kevin Kisner; Alexander Levy (Fra)

21:36: Matt Kuchar; Charl Schwartzel (SA)

21:48: Patrick Reed; Joost Luiten (Ned)

22:00: Tony Finau; Henrik Stenson (Swe)

22:12: Andres Romero (Arg); Brandt Snedeker

22:24: J.B. Holmes; Shane Lowry (Ire)

22:36: Cameron Smith (Aus); Louis Oosthuizen (SA)

22:48: Jordan Spieth; Branden Grace (SA)

23:00: Dustin Johnson; Jason Day (Aus)