The International Space Station's commander Peggy Whitson surpassed the record of 534 days, two hours and 48 minutes for most accumulated time in space by an American.
Whitson already was the world's most experienced spacewoman and female spacewalker and, at 57, the oldest woman in space.
By the time she returns to Earth in September, she'll have logged 666 days in orbit over three flights.
The world record, 879 days, is held by Russian Gennady Padalka.
Whitson broke the NASA cumulative record set last year by astronaut Jeffrey Williams; Scott Kelly holds the US record for consecutive days in space, 340.
Whitson is also the first woman to command the space station twice and the only woman to have led NASA's astronaut corps.
NASA astronaut Jack Fischer, who arrived at the space station last week and took part in Monday's call, said the space station is "by far the best example of international cooperation.''
Whitson told the president that spaceflight takes a lot of time and money, so getting to Mars will require collaboration from other countries to succeed.
NASA is building the hardware right now to test a new rocket that will carry astronauts farther from Earth than ever before, she said.
