Colin Montgomerie shares the clubhouse lead with little-known American Marco Dawson on 10-under par, with nine holes of their third round still to play in the Senior British Open on Saturday.

Poor light suspended play, five hours after the delayed start to the round. The second round, suspended on Friday because of rain, wasn't completed until Saturday mid-afternoon.

At that stage, Dawson led on 8 under, a shot clear of defending champion Bernhard Langer. Montgomerie was on 6 under alongside Fred Couples, Jeff Sluman, Miguel Angel Jimenez, and Peter Fowler.

The late start to the third round, and with 83 players making the cut, meant play began on the first and 10th tees at Sunningdale Old Course.

Montgomerie showed he meant business right from the start, birdieing the first three holes. Then he missed birdie chance after birdie chance before picking up his fourth at the ninth, when play was halted in the gathering gloom.

"I had a great start, and I'm really looking forward to tomorrow," said the Scot, who wants to add his home senior major to the three he has won in America so far.

Dawson also birdied the first, then parred all the way to the ninth, where he also picked up a shot.

"This is just a survival test now," Dawson said. "It was a long day, and it's going to be long again tomorrow."

The third member of the last group, Langer, also birdied the first, dropped a stroke at the fourth, and missed a birdie chance from two feet at the ninth to stay in a four-way for fifth on 7 under.

Couples, the champion at Turnberry in 2012, was at 8 under and in a share of third place with Ireland's Philip Walton.

Walton raced to the turn in 30 with five birdies. He dropped a shot at the 10th but picked up his sixth and seventh birdies to reach 8 under par, having started at 2 under, with one hole to play.

Tom Watson was five off the pace at 5 under after carding 66. With him was Jeff Maggert, bidding for his third senior major of the year. Maggert still had three more holes to play.

More rain was forecast on Sunday.