The "700 Club" host's feat is recounted on the Web site of his Christian Broadcasting Network in Virginia Beach.
Skeptical online commentators have been buzzing about it and experts have questioned it since Clay Travis of CBS SportsLine.com called the 2,000-pound assertion impossible in a column last month. Travis noted the leg-press record for football players at Florida State University is 665 pounds less.
A spokeswoman recently released a photo she said showed Robertson leg-pressing 2,000 pounds on Feb. 1, 2003. Robertson had successful surgery to remove a cancerous prostate gland later that month and turned 73 that March.
"I did it one time, one rep, but I had built up to it for about three years," Robertson said Wednesday in a telephone interview with The Associated Press, the first time he has spoken with a reporter since the leg-press brouhaha. He said he wanted to "clarify my purpose" because this has "been blown out of proportion and misunderstood."
Robertson said his doctor encouraged him to leg-press weights to strengthen his bad knees.
"We weren't trying to compete with 25-year-old bodybuilders," Robertson said. "We were merely trying to show seniors that they didn't have to spend time in a wheelchair or in a rocking chair in a nursing home, that they could live an active life."
"When I hit 570 pounds, it was a big deal," he recalled. "I called everybody in the gym to come look at what I'd done. Then one Saturday we went up to 800 pounds. Then later my doctor who was working with me got me up to 1,500. I went up 1,400, 1,500, 1,600, 1,700 ... in one day. The last time, it was one lift, I went 2,000 pounds."
"But I didn't do it with the same form that these professional bodybuilders do, which is a full squat, and it's very difficult," Robertson said. "But I did do it. I regularly can do 1,000 pounds and 1,200 pounds."
Robertson said he used an incline leg press and did "the full extension on that particular machine."
"They have a brake on it. I was told put the brake on," Robertson said. "When the professionals do it, they take the brake off and let the weight come all the way down on them. And if you don't have a lot of help, you've got a Volkswagen sitting on your hips. I didn't do that."
CBN's Web site has a video showing Robertson leg-pressing 1,000 pounds, with his hands pushing up on his thighs.
The Web site attributes Robertson's energy in part to "his age-defying protein shake." The site offers a free recipe for the shake, with ingredients including soy protein isolate, whey protein isolate, flaxseed oil and apple cider vinegar.
Robertson also has licensed his name to Columbus, Ohio-based Basic Organics Inc., which makes a product called "Pat's Diet Shake." Robertson said the shake is similar to his free recipe.
"We're selling the thing like crazy. There are thousands of people who want to get it. They think the shake had something to do with my ability to lift weights, and I don't think it did," he said, chuckling.
He added, though, that the shake "makes people strong and keeps them youthful."
Robertson said he has advocated a healthy diet and exercise for years. He takes about 45 vitamins and minerals daily, abstains from sweets and soft drinks, eats lot of salads, fruits and nuts and rides horses, plays golf and works out.