The top seed was swiftly followed into the winners’ circle by a restrained Andy Roddick, who this time let his tennis do all the talking in a brutal 6-1 6-3 6-3 demolition of Brazilian Flavio Saretta.
But Americans did not have it all their own way at their grand slam.
New Yorker James Blake was taught a lesson by an imperious Roger Federer, the second seed and Wimbledon champion winning 6-3 7-6 6-3, and in the women’s draw 17th seed Meghann Shaughnessy was walloped 6-2 6-4 by world number one Kim Clijsters.
Belgian top seed Clijsters will next meet fifth seed Amelie Mauresmo of France, who overpowered Thai Tamarine Tanasugarn 6-2 6-2 to reach the quarterfinals. Federer next meets David Nalbandian of Argentina.
Nalbandian, who leads Federer 4-0 in matches played, saw off Wimbledon runner-up Mark Philippoussis 7-5 6-7 6-3 6-2.
Earlier, third seed Lindsay Davenport became the first woman through to the quarters when she struggled past Russian Nadia Petrova 6-0 6-7 6-2.
Davenport, the 1998 U.S. Open champion, had a pain-killing injection in her toe before the season’s last grand slam, and she appeared to be moving gingerly towards the end of the one hour 52 minutes match.
Davenport will face Paola Suarez in the quarters. The 24th seed from Argentina beat Russian Elena Likhovtseva 6-2 3-6 7-5.
Having been accused by Croatia’s Ivan Ljubicic of influencing linesmen with his animated behaviour in an emotionally-charged second-round clash, Roddick was subdued throughout his 87-minute match.
His tennis certainly did not suffer, however, and he heads into the next match with Belgian Xavier Malisse a deserved favourite to win his first grand slam.
World number one Agassi barely put a foot wrong once his match, held over from Saturday night, resumed under cloudless skies with the American leading 6-3 0-1.
Twice a winner at Flushing Meadows and three-times runner-up, including last year, the 33-year-old Agassi underlined his determination to win a ninth grand slam with a top-notch performance.
His receiving radar will have to be fully functional in the next round, however, when he lines up opposite massive server Taylor Dent of the U.S.
Federer was in sublime form throughout his first foray under the floodlights, finishing off Blake in two hours.
In the second set alone Federer held 20 break points on the Blake serve, managing to convert only one.
The Swiss player’s late-night win meant for the first time since 1981 all of the top eight men’s seeds had made it through to the last 16 here.
Earlier, 22nd seed Younes El Aynaoui thrilled a Grandstand Court crowd with a pulsating 7-6 5-7 3-6 6-3 7-6 triumph over 10th-seeded Czech Jiri Novak.
The delighted Moroccan, whose wife Anne Sophie had the couple’s third son last week, ripped off his shirt and hurled his rackets into the crowd after clinching victory.
El Aynaoui meets Spain’s Carlos Moya in the fourth round.
Results (x denotes seed):
WOMEN’S (fourth round): Lindsay Davenport (USA x3) bt Nadia Petrova (RUS x19) 6-0, 6-7 (6/8), 6-2; Paola Suarez (ARG x24) bt Elena Likhovtseva (RUS) 6-2, 3-6, 7-5; Amelie Mauresmo (FRA x5) bt Tamarine Tanasugarn (THA) 6-2, 6-2; Kim Clijsters (BEL x1) bt Meghann Shaughnessy (USA x17) 6-2, 6-4
MEN’S (third round): Carlos Moya (Spa x7) bt Nicolas Massu (CHI) 7-5, 6-4, 3-6, 6-3; Younes El Aynaoui (MOR x22) bt Jiri Novak (CZE x10) 7-6 (7/1), 5-7, 3-6, 6-3, 7-6 (7/5); Andre Agassi (USA x1) bt Yevgeny Kafelnikov (Rus x28) 6-3, 7-6 (7/4), 6-4; Andy Roddick (USA x4) bt Flavio Saretta (BRA) 6-1, 6-3, 6-3; Sjeng Schalken (NED x12) bt Ivo Karlovic (CRO) 7-6 (10/8), 7-6 (7/5), 7-6 (7/3); Rainer Schuettler (GER x8) bt Alberto Martin (SPA) 6-1, 6-4, 6-2; David Nalbandian (ARG x13) bt Mark Philippoussis (AUS) 7-5, 6-7 (10/12), 6-3, 6-2; Xavier Malisse (BEL) bt Dmitry Tursunov (RUS) 7-5, 6-4, 7-6 (10/8); Roger Federer (SWI x2) bt James Blake (USA) 6-3, 7-6 (7/4), 6-3.—Reuters/AFP