WASHINGTON — President Biden came into office promising to tackle the planet’s climate crisis. But rising gas prices, driven in part by Russia’s invasion of Ukraine, have pushed the environmental-minded president to do something unlikely: embrace oil.

On Tuesday, Mr. Biden traveled to Iowa, where he announced that the Environmental Protection Agency would temporarily lift regulations prohibiting the summertime use of an ethanol-gasoline blend known as E15, which contributes to smog during the warmer months. Mr. Biden said his government was going to waive the regulation in order to lower the price of gasoline at the pump for many Americans.

“It’s going to help some people and I’m committed to whatever I can do to help, even if it’s an extra buck or two in the pockets when they fill up, make a difference in people’s lives,” Mr. Biden said after taking a tour of a facility that produces 150 million gallons of bioethanol a year. He added later: “When you have a choice, you have competition. When you have competition, you have better prices.”

The ethanol announcement is the latest move by Mr. Biden’s White House that runs counter to promises he made as a presidential candidate to pivot the United States away from fossil fuels. The price of gas, it seems, has changed his calculus. The average cost of a gallon of gas last October was $3.32; in March, it was about $4.32.

Last month, the president proposed a new policy aimed at pressuring oil companies to drill for oil on unused land, saying the companies have thousands of “permits to dig oil if they want. Why aren’t they out pumping oil?” Mr. Biden also announced the sale of 180 million barrels of oil from the country’s strategic petroleum reserve over the next six months, the largest-ever release in history.

“It will provide a historic amount of supply for a historic amount of time,” Mr. Biden said then.

Mr. Biden has walked a careful tightrope in the weeks since U.S. sanctions on Russian oil and gas sent energy prices soaring. Even as he has implored oil producers to pump more crude, the president has sought to assure his political base that meeting the needs of today’s crisis won’t distract from the longer-term goal of moving away from the fossil fuels that drive dangerous climate change.

The president’s embrace of oil underscores his awkward position between two competing priorities: the imperative to reduce America’s use of fossil fuels and the pressure to respond to the rising price of gas.

“I don’t think when his term started Joe Biden thought he would be spending his second year tapping the strategic petroleum reserve or flying off to Des Moines to approve E15 waivers,” said Barry Rabe, a professor of political science and environmental policy at the University of Michigan.

With his broader climate change agenda and investments in wind, solar and electric vehicles largely stalled in Congress, the president’s allies say that his short-term, pro-oil actions could further disillusion the environmentally-focused voters whom Democrats need to turn out for congressional elections this fall.

“Climate voters are likely to be underwhelmed, barring a major legislative achievement,” Mr. Rabe said.

Mr. Biden’s recent actions have prompted criticism in many parts of the environmental community. Mitch Jones, managing policy director for the lobbying arm of the nonprofit group Food & Water Watch, said in a statement that the decision to waive the summertime ban on E15 is “driving us deeper into the hole of dirty fossil fuel mixtures.”

White House officials disputed the idea that Mr. Biden has shifted to embrace fossil fuels. They note that his environmental policies have always envisioned a continued reliance on oil and gas while the country makes a yearslong transition to cleaner energy sources.

And they said the current energy crisis is a stark example of why they believe Congress and Republicans should support moving to alternate forms of energy and reducing U.S. dependence on oil.

“Families need to take their kids to school and go to work, get groceries and go about their lives — and sometimes that requires gas today, this month and this year,” said Vedant Patel, a White House spokesman. “But at the very same time we must speed up — not slow down — our transition to clean energy.”

In recent weeks, Biden administration officials have announced funding to make homes energy efficient, launched a new conservation program and said the president would invoke the Defense Production Act to encourage domestic extraction and processing of minerals required to make batteries for electric vehicles.

Republicans and lobbyists for the oil and gas industries have sought to blame high gas prices on Mr. Biden’s climate agenda, arguing that prices would be lower if the White House had not pursued programs aimed at moving the country toward other forms of clean energy.

“Don’t blame the gas prices on Putin,” Senator Mitch McConnell of Kentucky, the Republican leader, said earlier this month on Fox News.

He added: “It is a reaction to the shutdown of the fossil fuel industry. They go after them in every single conceivable way.”

But in reality, Mr. Biden has had limited success putting his climate agenda in place — in large part because of opposition from Republicans and the energy industry. So experts say it is difficult to blame the higher gas prices on the effects of those proposals, which have yet to be enacted.

For example, Mr. Biden proposed $300 billion in tax incentives to galvanize markets for wind and solar energy and electric vehicles. If enacted, it could cut the nation’s emissions roughly 25 percent by 2030. That legislation passed in the House, but stalled in the Senate amid opposition from Republicans and Senator Joe Manchin, Democrat of West Virginia.

Mr. Biden also has sought to suspend new oil and gas leases on federal lands and waters, a move the oil industry has maintained hurt production. Yet that policy was stopped by the courts and Mr. Biden last year auctioned off more than 80 million acres in the Gulf of Mexico — the largest lease sale in history.

Officials estimated that allowing the ethanol blend to be sold in the summer would shave 10 cents off every gallon of gasoline purchased at the approximately 2,300 stations in the country that offer it, and cast the decision as a move toward “energy independence.”

That is a small percentage of the 150,000 gas stations across the country, according to NACS, the trade association that represents convenience stores.

Mr. Biden also faces growing pressure to bring down energy prices, which helped drive the fastest rate of inflation since 1981 in March. A gallon of gas averaged $4.10 on Tuesday, according to AAA.

Ethanol is made from corn and other crops and has been mixed into some types of gasoline for years to reduce reliance on oil. But the blend’s higher volatility can contribute to smog in warmer weather. For that reason, environmental groups have traditionally objected to lifting the summertime ban. So have oil companies, which fear greater use of ethanol will cut into their sales.

How much the presence of ethanol holds down fuel prices has been a subject of debate among economists. Some experts said the decision is likely to reap larger political benefits than financial ones.

“This is still very, very small compared with the Strategic Petroleum Reserve Release,” said David Victor, a climate policy expert at the University of California, San Diego. “This one is much more of a transparently political move.”

And the environmental benefits of biofuels are undercut by the way they push up prices for corn and food, some energy experts argue.

Corn state lawmakers and industry leaders have been urging Mr. Biden to fill the gap created by the United States ban on Russian oil exports with biofuels. Emily Skor, CEO of the biofuel trade association group Growth Energy, called the decision “a major win” for energy security.

“These are tough choices and I don’t think it’s anything they relish,” said Tiernan Sittenfeld, the senior vice president for government affairs at the League of Conservation Voters, a nonprofit group. “I do believe they are working to do it in a way that does not lock in decades more fossil fuel infrastructure or pollution, and I think they remain determined as ever to meet the moment on climate.”