WASHINGTON, April 19 (AFP) - The United States will press all nations to reduce reliance on coal, Secretary of State Antony Blinken said on Monday (Apr 19), in an implicit challenge to China as he vowed greater US leadership.

Blinken kicked off a week of intense climate diplomacy by President Joe Biden, who has invited 40 world leaders to a virtual summit Thursday and Friday aimed at raising the world's ambitions on climate.

Casting climate change as a national security issue, Blinken warned both of major impact around the planet - and risks to the United States if it does not raise its own efforts.

"It's difficult to imagine the United States winning long-term strategic competition with China if we cannot lead the renewable energy revolution," Blinken said in a speech in Annapolis, Maryland.

"Right now, we're falling behind."

While Blinken pointed to China's lead on solar and other technology, the Asian power is also the world's largest emitter of carbon blamed for climate change - and by far the biggest user of coal, the dirtiest form of energy.

"Our diplomats will challenge the practices of countries whose action - or inaction - is setting us back," Blinken said.

"When countries continue to rely on coal for a significant amount of their energy, or invest in new coal factories, or allow for massive deforestation, they will hear from the United States and our partners about how harmful these actions are."

China, despite a pledge to go carbon neutral by 2060, has moved ahead with coal-powered plants, only modestly increasing ambitions for renewables in its latest five-year development plan.

Coal is also a sensitive issue in the United States which under former president Donald Trump left the Paris climate accord as he declared himself a champion of miners, although demand for coal has kept falling.