The sixth-seeded Agassi held off the tenacious third-seeded Austrian with a barrage of winners for a 6-2, 7-5, 4-6, 6-2 victory to take his place in the semi-finals for the sixth time.
"I knew with his style of play and my style of play that it was gong to be important to be nothing but mentally committed to running for every ball and really playing a high level of tennis." Agassi said after the two hour 32 minute slugging match.
Agassi spent most of the match on the baseline, controlling the points by hitting his groundstrokes from corner to corner. "One thing Thomas does well is that he likes to dictate play. The one thing that I had to do was definitely get on the offence," said Agassi, who hit 48 winners to Muster's 27.
After being outclassed in the opening two sets, Muster fought back from 2-0 down to take the third set. Muster led for the first time since the opening game when Agassi dropped his serve on a double fault at 3-3. The Austrian held for 5-3 and then served out the set from 0-30. However, any momentum that Muster had on his side was washed away when a few sprinkles of rain forced officials to stop play after Agassi held serve to start the last set.
Though the players never left the court and were back playing within five minutes, the respite seemed to be just what Agassi needed to energise a final winning spurt. "That could have been a turning point," Muster, who fell behind 3-0 before holding serve, said.
The two criticised each other throughout the year, and the friction heightened the atmosphere surrounding this encounter more than any of their previous eight meetings, which they had split 4-4.
Muster was one of the most vocal critics of the Open's decision to elevate Agassi two places in the seedings from his ATP ranking and drop the Austrian one spot from his ranking. On Tuesday, Muster had criticised Agassi's coach, Brad Gilbert, whom he claimed was universally disliked on the tour.
Earlier in the year, Agassi questioned Muster's legitimacy as the world No 1 since Muster's climb in the rankings had been due to his superiority on one surface, clay.
In the women's event Steffi Graf reached her 11th US Open semi-final by beating the unseeded Austrian, Judith Wiesner, 7-5, 6-3, and will now play Martina Hingis, the Swiss teenager who became only the third 15-year-old to reach the last four after beating the seventh seed from the Czech Republic, Jana Novotna, 7-6, 6-4. The other two were Andrea Jaeger in 1980 and Jennifer Capriati in 1991.
The other semi-final today is between Monica Seles and the fourth seed, Conchita Martinez.
Tim Henman, the British No 1, has pulled out of next week's Bournemouth International Open because of thigh and groin injuries, and is also doubtful for Britain's Davis Cup match against Egypt later this month. Henman has had to bow to the injuries for which he received painkillers during his run to the last 16 before losing to Stefan Edberg at the US Open in New York this week.Reuse content