Cincinnati - Novak Djokovic's third-round fightback against defending champion Grigor Dimitrov was interrupted by rain as the pair stood one set each on Thursday at the ATP-WTA Cincinnati Masters.
Former world number one Djokovic is vying to break through for a first Cincinnati win after coming up empty in five finals. He lost the first set 6-2 and won the second 6-3.
Cincinnati remains the only one of the nine Masters 1000 events that the Serb star hasn't won. He has lifted trophies at least twice at each of the other eight events in the elite ATP series.
Djokovic is also trying to avoid an unenviable record of 30 Cincinnati match wins without a title.
Bulgaria's Dimitrov, who has won just one of eight prior encounters with Djokovic, prevailed easily in the opening set and broke early in the second before Djokovic roared back, breaking for a second time to take a 5-3 lead.
The 10th-seeded Serb squared the match as the day's second bout of major rain moved in.
Earlier, Simona Halep and Juan Martin del Potro completed rain-delayed second-round victories.
World number one Halep took advantage of an early afternoon respite from the weather to finish off a 4-6, 6-3, 6-3 victory over Ajla Tomljanovic.
Halep, clearly frustrated when the match was halted at 3-3 in the third on Wednesday night, won three straight games to finish off the victory in 10 minutes.
The timing was perfect for the French Open champion as drizzle resumed moments after her contest ended.
Argentina's world number three del Potro had played just six points in the first game of his postponed second-round match against Chung Hyeon before the rain came again.
But the weather cleared, allowing officials to get eight courts into action, and del Potro returned to finish off a 6-2, 6-3 win over the South Korean to set up a night meeting with Australian Nick Kyrgios for a place in the quarter-finals.
Milos Raonic reached the men's quarter-finals with a 7-6 (8/6), 6-4 victory over fellow Canadian Denis Shapovalov, avenging a loss to his younger compatriot in Madrid three months ago.
In women's third-round action, reigning US Open champion Sloane Stephens was eliminated while Madison Keys, runner-up at Flushing Meadows last year, moved ahead.
Belgian Elise Mertens scored the second top five win of her career, beating Stephens 7-6 (10/8), 6-2 while Keys rallied to defeat fourth-seeded Wimbledon champion Angelique Kerber 2-6, 7-6 (7/3), 6-4.
Keys fired 55 winners with 44 unforced errors against the German, who is playing her first hardcourt tournament in the build-up to the US Open.
"I had to keep it cool, she gets lot of balls back," Keys said. "I used my forehand and serve well today. I'm really happy and I'm looking to go further."
Keys next faces Aryna Sabalenka of Belarus, who upset French sixth seed Caroline Garcia 6-4, 3-6, 7-5.
Petra Kvitova, who toppled Serena Williams in the second round, reached the last eight with a 6-4, 6-2 win over France's Kristina Mladenovic.
"I just need to get out there and really fight, I was telling myself to fight," the two-time Wimbledon champion said.
"I did a lot of talking to myself today, pushing myself to just go for it. I'm glad that in the important points I played aggressively - that was important today."
Results from the ATP and WTA Cincinnati Masters tournament on Thursday (x denotes seeding):
Juan Martin del Potro (ARG x4) bt Chung Hyeon (KOR) 6-2, 6-3
Milos Raonic (CAN) bt Denis Shapovalov (CAN) 7-6 (8/6), 6-4
Pablo Carreno-Busta (ESP x13) bt Robin Haase (NED) 6-4, 6-2
Simona Halep (ROM x1) bt Ajla Tomljanovic (AUS) 4-6, 6-3, 6-3
Amanda Anisimova (USA) bt Petra Martic (CRO) 6-4, 6-3
Lesia Tsurenko (UKR) bt Ekaterina Makarova (RUS) 7-6 (7/5), 6-2
Madison Keys (USA x13) bt Angelique Kerber (GER x4) 2-6, 7-6 (7/3), 6-4
Aryna Sabalenka (BLR) bt Caroline Garcia (FRA x6) 6-4, 3-6, 7-5
Petra Kvitova (CZE x8) bt Kristina Mladenovic (FRA) 6-4, 6-2
Elise Mertens (BEL x15) bt Sloane Stephens (USA x3) 7-6 (10/8), 6-2