Mexico City: Brendon Todd, coming off a victory two weeks ago in Bermuda, shared the lead with fellow American Vaughn Taylor on Sunday when darkness halted the final round of the US PGA Mayakoba Classic.
Taylor and Todd, both on 20-under par with four holes to finish, were among seven top-10 players yet to finish their final round when sunset fell at Playa del Carmen, Mexico.
Mexico's Carlos Ortiz and American Harris English were on 19-under, Ortiz with one hole to play and English with four remaining. American Adam Long was on 18-under with three holes remaining.
Competition will resume at 7:30 a.m. local time (1230 GMT) with 12 players set to complete their 72 holes after heavy rains washed out play Thursday.
To win, it might take matching or breaking the 72-hole tournament record of 22-under par set last year by Matt Kuchar.
Todd seized the lead with a six-under par 65 in Sunday's third round and players went directly into the last round, rushing in a failed bid to complete 36 holes on the final day.
Todd, 34, won his first US PGA crown at the 2014 Byron Nelson Championship then ended a five-year win drought during which he battled the full-swing yips by taking the Bermuda Championship two weeks ago. This is his first start since that triumph.
"I feel great about my game. Happy to have a chance to win this after winning in Bermuda," Todd said. "I'm excited for the opportunity."
Taylor, 43, seeks his fourth PGA title after taking the 2004 and 2005 Reno-Tahoe Opens and the 2016 Pebble Beach Pro-Am.
"I'm just trying to hang in there best I can," Taylor said. "Didn't feel too great. I'm tied for the lead. I'm pleased."
Taylor birdied the third hole in his final round, made back-to-back birdies at the ninth and 10th holes and sank another at the par-5 13th.
Todd birdied the par-3 fourth, par-5 seventh and par-4 ninth and 12th holes to stay on top but could only par the 13th and took a bogey at 14 in the twilight before stopping on the 15th green alongside Taylor.
"I wanted to hit it in there close and come back tomorrow and make a birdie," Todd said.
"There was probably no benefit to me playing after making two fives in a row." While his playing partners raced to the 18th tee so they could finish, Ortiz decided against teeing off on the final hole due to the darkness.
"The last shot, it was hard to see," Ortiz said.
"The decision I took not to play, I think was the right one. I have a really good chance to win. Winning in front of my family and crowd would be a dream come true."
Kuchar made a hole-in-one on the par-3 eighth hole in the final round while US compatriot Brian Gay aced the par-3 10th hole.