WASHINGTON (AFP) - US President Barack Obama on Tuesday launched a push to get girls interested in science and technology, warning the country would miss out if it did not attract women to those fields.

"There's so much talent to be tapped if we're working together," Mr Obama said at the annual White House Science Fair, where students from elementary to high school present winning projects.

"Right now, fewer than one in five bachelor's degrees in engineering or computer science are earned by women. Fewer than three in 10 workers in science and engineering are women," the president said.

"That means we've got half the field - or half our team we're not even putting on the field. We've got to change those numbers."

He called science, technology, engineering and math the "fields of the future, where the good jobs are going to be," adding: "I want America to be home for those jobs."

Mr Obama enthusiastically focused on each display for about an hour, hailing the students' ingenuity.

One 18-year-old girl researched the genetics behind a rare form of liver cancer from which she suffers herself; a 12-year-old boy invented better sand bags used to shore up vulnerable homes in floods and hurricanes.

A group of elementary school girls used Lego bricks to show off their design for a so-called "flood-proof" bridge.

"We're blessed to live in a country filled with bright, eager young people who love science, love tinkering, love making things, who have the ability to see old problems and grand challenges with fresh eyes," Mr Obama said.

"And those of us who are grown-ups have an obligation to help them reach their full potential, just as others helped us."