Czech Lukas Rosol and his bid to win back-to-back Winston-Salem Open titles remains on track after overcoming Ernests Gulbis to reach the second round on Monday.

Rosol was a 6-4 7-6 (7-4) over former world number 10 Gulbis in North Carolina, which hosts the final lead-up event before the US Open starts next week. 

Rain caused problems at the ATP 250 event, with three scheduled second-round matches - Sam Groth versus Steve Johnson, Benoit Paire against Hyeon Chung and Diego Schwartzman's clash with Pablo Andujar - postponed to Tuesday.

But Rosol, who will face Jerzy Janowicz in the second round in a re-match of the 2014 final, was able to complete his clash with Latvian Gulbis after he sent down 14 aces in one hour, 39 minutes.

Qualifier Martin Klizan made it through his first-round meeting with Marsel Ilhan, notching a 7-6 (7-1) 6-2 victory.

Klizan will next face 11th seed Jiri Vesely.

Australian teen Thanasi Kokkinakis required three match points to upset Alexandr Dolgopolov 7-6 (7-1) 7-6 (7-5).

Next up for Kokkinanis is 15th seed Teymuraz Gabashvili.

Aljaz Bedene earned a second-round match against top seed Gilles Simon via his 6-2 6-2 win over Marco Cecchinato.

Seventh seed Sam Querrey will open his campaign against Simone Bolelli, who accounted for Federico Delbonis 6-4 6-3.

Pierre-Hugues Herbert downed 2010 champion Sergiy Stakhovsky 6-3 6-2 to earn a match-up with 14th seed Marcos Baghdatis.

Malek Jaziri defeated Joao Souza 6-3 6-4, Frances Tiafoe edged out James Duckworth 3-6 7-6 (7-4) 7-6 (7-3), Denis Istomin dismissed Donald Young 6-3 6-3 and Pablo Carreno Busta ousted veteran Tommy Haas 6-3 6-4 in other first-round results.

Jaziri, Tiafoe, Istomin and Carreno Busta will now meet seeds Viktor Troicki, Thomaz Bellucci, Jo-Wilfried Tsonga and Joao Sousa respectively.

Meanwhile, the only second-round contest completed on Monday saw Borna Coric rally to beat Santiago Giraldo 4-6 6-2 6-2.