United Nations ? With tales of rising seas and talk of human solidarity, world leaders at the first United Nations climate summit sought Monday to put new urgency into global talks to reduce global-warming emissions.

What’s needed is “action, action, action,” California’s environmentalist governor, Arnold Schwarzenegger, told the assembled presidents and premiers.

The Bush administration showed no sign, however, that it would reverse its stand against mandatory emission cuts endorsed by 175 other nations. Some expressed fears the White House, with its own forum later this week, would launch talks rivaling the U.N. climate treaty negotiations.

President Bush didn’t take part in the day’s sessions, which drew more than 80 national leaders, but attended a small dinner Monday evening, a gathering of key climate players hosted by Secretary-General Ban Ki-moon.

Ban set the day’s theme in his opening address, declaring that “the time for doubt has passed” on the issue of global warming. At the day’s end, he said he believed the scores of speeches showed a “major political commitment” to success in the global talks.

Throughout, in remarks clearly aimed at Washington, the U.N. chief described the U.N. negotiating umbrella as “the only forum” where the issues can be decided.

Ban organized the one-day summit to build momentum for December’s annual climate treaty conference in Bali, Indonesia, when Europe, Japan and others hope to initiate talks for an emissions-reduction agreement to succeed the Kyoto Protocol in 2012.

The 175-nation Kyoto pact, which the U.S. rejects, requires 36 industrial nations to reduce carbon dioxide and other heat-trapping gases. It set an average target of a 5 percent cut below 1990 levels by 2012 for emissions from power plants and other industrial, agricultural and transportation sources.

Advocates for emissions reductions say a breakthrough is needed at Bali to ensure an uninterrupted transition from the 1997 Kyoto pact to a new, deeper-cutting regime, something that almost certainly would require a change in the U.S. position.

The chief U.N. climate scientist, Rajendra Pachauri, told the summit of the mounting evidence of global warming’s impact, including the accelerating rise in sea levels as oceans expand from heat and the runoff of melting land ice.

“The time is up for inaction,” he said.

A Pacific islander, President Emanuel Mori of the Federated States of Micronesia, told the summit that encroaching seas are already destroying crops, contaminating wells and eating away at his islands’ beaches.

“How does one explain to the inhabitants that their plight is caused by human activities done in faraway lands?” he asked.