at Atlanta in another hard-court tournament that's a tuneup for the U.S. Open.
After dropping Saturday's first set, Isner was ahead on serve 2-1 in the second when, with the match 70 minutes old and a drizzle falling, play was suspended. When they resumed at 30-40, Isner converted the break point with a forehand passing winner on a 12-stroke exchange.
That was the first break of serve in the match, and all the 20th-ranked Isner would need to even things at a set apiece 15 minutes later. He then broke again to lead 3-2 in the third, this time at love, helped by three unforced errors by the 61st-ranked Tursunov.
That was pretty much that, because Isner's powerful serve was clicking - just as it usually does during the summer hard-court season in North America.
"It's my absolute favorite time of the year," said Isner, whose best Grand Slam showing was a run to the US Open quarterfinals in 2011. "It's not a coincidence that I play and do well here in the summer, every single year."
Isner won 69 of 86 points he served Saturday, including runs of 16 and 14 in a row, and did not face a break point. Despite consistently hitting serves at 130 mph or faster, Isner only double-faulted once. Tursunov hit nine double-faults and only four aces.
In Sunday's final, Isner will face top-seeded Juan Martin del Potro, the 2008 and 2009 champion in Washington, or No. 3-seeded Tommy Haas. They were to meet in the second men's semifinal; both women's semifinals also were scheduled for Saturday night.
"I've got one more tomorrow, and I'm going to give it my all," said Isner, who was visited by a trainer but said the left thigh muscle injury that forced him to stop playing at Wimbledon was "not bothering me at all."
If he wins Sunday, Isner would earn his third title of 2013 and pull even with No. 1 Novak Djokovic for the third-highest total on tour. Only Rafael Nadal (seven) and Andy Murray (four) have won more tournaments this season.
As well as Isner served in the first set Saturday, he lost it in a tight tiebreaker - exactly the way he began his quarterfinal against Marcos Baghdatis before coming back to win in three sets.
Isner, the 2007 runner-up in Washington, won 24 of 28 service points at the start of the match against Tursunov, but faltered in the tiebreaker, when he went only 5 for 8.
The highest-ranked American man actually held the match's first set point, ahead 6-5, but sailed a return long. Tursunov's first set point came at 7-6, and Isner erased it with a 142 mph ace. But he wouldn't win another point in the tiebreaker, missing a volley long, then watching Tursunov end an 11-stroke exchange with a forehand volley winner.
After trudging to the sideline, Isner dropped his racket and white baseball hat on the ground and covered his face with a towel.
There were more missed opportunities for Isner early in the second set, including a break point at 1-0, when he missed a backhand long and yelled, "No!"
The next time Tursunov served, though, the Russian made a bad error, dumping an overhead smash into the net to fall behind 15-40 and create two more break points. Isner couldn't capitalize on the first, putting a forehand return of a 94 mph serve into the net. That's when play was halted because of the rain, leading to a delay of about 1 hour, 20 minutes.
When they returned to the court, Isner did not take long to assert himself.