On Tuesday, the opening night of the meet, Ledecky qualified for the 800m freestyle in a year's best time and is also qualified for the 1,500m.
Should Ledecky, who won four golds at the Rio Olympics, finish in the top two in Friday's 400m free, she will be in line to contest six events in Budapest, including relays, for her busiest schedule yet at an Olympics or worlds.
"I’ve been slightly improving throughout the spring," said Ledecky. "I’m certainly growing my confidence in this race."
Olympic champion Ryan Murphy won the national title in the men's 200m backstroke while Townley Haas earned his first individual national title with a decisive win in the men's 200m freestyle.
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Kevin Cordes won the 200m breaststroke while Caeleb Dressel claimed his first national title in the men's 50m butterfly and qualified for his second event after already earning a spot in the 100m freestyle.
Olympic 100m breaststroke champion Lilly King set a personal best of 2:21.83 in winning the women's 200m breaststroke to qualify for her first world championships roster.
"I’d gone 2:24 six times since last December, so I was ready for that breakthrough. Luckily it came tonight," King said. "I knew I had that in me."
Kathleen Baker won the 200m backstroke in a year's best 2:06.38, while Kelsi Worrell won the women's 50m butterfly.
(Reporting by Larry Fine in New York; Editing by Peter Rutherford)
