WASHINGTON — U.S. Energy Secretary Steven Chu warned Monday that the United States is at risk of slipping behind China as the world’s leading innovation hub unless it steps up its commitment to clean energy research and development.

Rattling off a string of discouraging economic trends for the United States, Chu said during a speech at the National Press Club that the country is at a juncture similar to the “Sputnik moment” of the late 1950s, when the Soviet Union vaulted to an early lead in satellite and rocket technology.

“The United States has been, for over a century, the greatest innovation machine in the world,” said Chu, the former director of the Department of Energy’s Lawrence Berkeley National Laboratory. “Today, this leadership is at risk.”

Whether Chu and President Obama can summon the kind of massive national response they believe is needed is far from assured. Still, Chu cast the issue as one of economic survival, and he said maintaining the country’s pre-eminence in science and technology has long had bipartisan support.

The evidence that the United States is falling behind is clear, he said. In recent years, China has raced ahead in high-tech exports and investment in alternative energy – spending that has yielded major advances in solar and coal technology, Chu said. 2020, nearly one-fifth of China’s energy supply is expected to come from alternative sources.

Though the federal stimulus bill included tens of billions of dollars for clean energy initiatives, the question is what happens once that money runs out, Chu said. Stimulus funds aside, the United States is spending just 0.14 percent of its federal budget on energy-related R&D, a proportion that he said has dropped steadily from about 8 percent in the early 1980s.