Praising the work of young scientists and inventors at the third White House Science Fair, President Obama on Monday announced a broad plan to create and expand federal and private-sector initiatives designed to encourage children to study science, technology, engineering and mathematics.

After browsing the 30 or so projects on display in the White House’s public rooms and the East Garden, Mr. Obama said he was committed to giving students the resources they need to pursue education in the disciplines, collectively known as STEM. Earlier, the White House announced efforts aimed at increasing participation in those fields, particularly among female and minority students, as well as those from low-income and military families.

“This is not the time to gut investments that keep our businesses on the cutting edge, that keep our economy humming, that improve the quality of our lives,” Mr. Obama told an audience in the East Room that included 100 students from 40 states, business leaders and science-minded celebrities, among them Bill Nye, the television host and science educator, and LeVar Burton, who appeared in “Star Trek: The Next Generation.”

“This is the time to reach a level of research and development that we haven’t seen since the height of the space race,” he said.