COLLEGE PARK, Md. - Michael Phelps inched ever closer to Ian Thorpe's world record in the 200m free Thursday night at the ConocoPhillips National Championships.

Phelps, 18, of the North Baltimore Aquatic Club set the American record in that event with a time of 1:45.99, winning his 13th U.S. national title and becoming the first American to swim it under 1:46. It was the second-fastest time in the world this year, behind Thorpe's 1:45.14 at World Championships.

Phelps was 1.05 seconds ahead of American record pace at the 150-meter mark, bringing the sold-out crowd to its feet.

"I did what I wanted to do, split what I wanted to split, but the last few meters I was struggling a little bit," Phelps said. "I felt my hands slipping a little bit, but I wanted to break 1:46, and I did that."

Thursday's swim marked the seventh time in less than a month that the phenom has set an American record.

"My goal is to get as many best times as possible, get as many records as possible, so I go out and swim as fast as I can every race," Phelps said. "I'm treating this like the World Championships, coming up to the blocks with everything I have in mind for those races."

In other races, Kaitlin Sandeno, 20, of Trojan Swim Club walked away with her second national title of the week with a time of 4:40.82 in the 400m IM. Sandeno led from start to finish and outdistanced her next closest competitor by about five and a half seconds.

Her time was the third-fastest in the world this year.

"It's been a while since I've gone to Nationals and swum a full load and felt good and not been sick," Sandeno said. "I had goals for myself that were a little faster than that, but I have to keep it in perspective. You've always got to be happy with a National title. I wish it was a little quicker, but I'll take it."

Canadians Brittany Reimer and Brian Johns won the other two individual events of the night, with Reimer taking the 200m free with a time of 2:00.62. Johns out-dueled Kevin Clements down the stretch to win the 400m IM with a time of 4:17.04.

Clements, 23, of North Baltimore finished second in 4:17.39.

"I really tried to swim it like a good 400 IMer and back-half it each leg, but I got caught taking it a little too easy on the backstroke," Clements said. "I was concentrating on bringing my strong points out in the breast and the free, and I just couldn't get him in the end there".

"(I learned) I need to get up there and really race the first 200. I hope I can do it next time."