Facing the disintegration of his climate agenda as ferocious heatwaves hit large parts of the world, Joe Biden has unveiled a new plan to push billions of dollars to US cities and states to help them cope better with extreme heat.

The president stopped short, however, of declaring a climate emergency.

Biden outlined the new actions in a speech on Wednesday at a former coal plant in Massachusetts, which is now part of an offshore windfarm project.

“As president, I have a responsibility to act with urgency and resolve when our nation faces clear and present danger,” Biden said. “And that’s what climate change is about. It is literally, not figuratively, a clear and present danger. The health of our citizens and our communities is literally at stake.”

The initiatives are aimed at helping salvage the president’s tattered climate agenda, which has endured a torrid month.

Last week, Joe Manchin, a West Virginia Democratic senator who owns a coal company, appeared to rule out supporting a new clean energy bill, seemingly dooming it in the evenly split Senate.

The blow arrived just two weeks after the conservative-dominated supreme court restricted the ability of the federal government to curb emissions from power plants.

Biden, speaking from a lectern set up on a rock pile to an audience that included Democratic legislators, said: “Climate change is literally an existential threat to our nation and to the world. So my message today is this: since Congress is not acting as it should – and these guys here are, but we’re not getting many Republican votes – this is an emergency. An emergency. And I will look at it that way.”

Biden’s actions include $2.3bn in funding to help communities prepare for heatwaves, droughts and floods, new guidance that allows the federal government to help provide cooling centers and air conditioning, and new planned offshore wind energy leases for the Gulf of Mexico coast.

“Right now, there are millions of people suffering from extreme heat at home so my team is also working with the states to deploy $385m right now. For the first time, states will be able to use federal funds to pay for air conditioners in homes, set up community cooling centres in schools where people can get through these extreme heat crises.”

The stakes of inaction on the climate crisis have been made starkly apparent this week, with more than 100 million Americans in grip of a dangerous heatwave that has pushed temperatures as high as 115F (46C) in parts of the country.

Elsewhere, disastrous wildfires have strafed France, Spain and Portugal, and the UK has endured its first ever recorded day of 40C heat.

The White House said the heatwaves showed the climate crisis is a “clear and present danger” to the US.

Climate campaigners hoped Biden would declare a climate state of emergency. Karine Jean-Pierre, the White House press secretary, said that wouldn’t happen on Wednesday but added that the option is “still on the table”.

The lack of such a declaration, or any sweeping ban of oil and gas drilling on public lands, is unlikely to satisfy those who have called for more vigorous action.

“Biden must declare a climate emergency, ban crude oil exports and halt new fossil fuel infrastructure, including pipelines and export terminals,” said Wenonah Hauter, executive director of Food & Water Watch.

“The clock is rapidly ticking towards inevitable, irreversible climate catastrophe. There is no more time to lose.”

Some Democrats have urged the president to declare a national emergency, which would allow him to block crude oil imports or direct the military to work on renewable energy production.

“For too long we have been waiting for a single piece of legislation, and a single Senate vote, to take bold action on our climate crisis,” a group of senators including the leading progressives Bernie Sanders and Elizabeth Warren, wrote to Biden this week.

“As a result, we urge you to put us on an emergency footing and aggressively use your executive powers to address the climate crisis.”

But it is unclear whether such an extraordinary use of presidential powers, normally used in a military context, would survive if challenged in the rightwing-dominated supreme court, or if it would be enough to make a significant dent in planet-heating emissions.

“Declaring a climate emergency doesn’t lower any emissions,” conceded Sheldon Whitehouse, a Democratic senator from Rhode Island. “You have to move on to acting like it’s a climate emergency, and I’m looking forward to those steps.”

Biden may take further action this week by directing new regulations to cut pollution from cars, trucks and power plants.

But the window of opportunity to avoid disastrous climate change is rapidly closing.

Scientists have said the world must slash emissions in half this decade, and phase them out entirely by 2050, if catastrophically worse heatwaves, floods, drought and other climate impacts are to be averted. The US will fall about halfway short of such a goal absent any significant congressional action, even with presidential orders, analysts have forecast.

“President Biden cannot do it alone,” said Heather Zichal, chief executive of the American Clean Power Association. “We urge Congress to get back to the table and come to a consensus on clean energy provisions that our country so desperately needs.”

Biden’s remarks on Wednesday were attended by political allies including John Kerry, the special presidential envoy for climate; Massachusetts senators Warren and Ed Markey; Whitehouse of Rhode Island and Massachusetts congressmen Jake Auchincloss and Bill Keating.

The president promised executive actions in the coming weeks. “When it comes to fighting climate change, I will not take no for an answer. I will do everything in my power to clean our air and water, protect our people’s health, to win the clean energy future.”

In an unexpected digression, he also recalled growing up in Claymont, Delaware, near polluting oil refineries. “You had to put on your windshield wipers to get literally the oil slick off the window. That’s why I and so damn many other people I grew up have cancer.”

The White House released a health summary from Biden’s doctor last November that said: “He has had several localized, non-melanoma skin cancers removed with Mohs surgery before he started his presidency.”

Climate activists applauded Biden’s pledge to do more to tackle global heating but some lamented the lack of an emergency declaration.

“President Biden’s announcements, while welcome, don’t even scratch the surface of what’s needed and what communities suffering most are demanding,” said Collin Rees, US program manager at Oil Change International. “Biden’s climate legacy hangs in the balance – we’re in desperate need of bold leadership, not tinkering around the edges while the world burns.”Varshini Prakash, executive director of the youth-led Sunrise Movement, added: “Young people are tired of receiving scraps from our government. President Biden must immediately declare a climate emergency, and do everything in his executive power to confront the climate crisis.”