ROME—President Biden said on Sunday he believed he would meet his target of halving U.S. emissions by the end of the decade, expressing confidence that Democrats’ social-spending and climate legislation would pass.

While the president touted G-20 efforts to address climate change, he singled out Russia, China and Saudi Arabia for opposing stronger global climate efforts and standing in the way of a stronger statement on the issue.

G-20...

ROME—President Biden said on Sunday he believed he would meet his target of halving U.S. emissions by the end of the decade, expressing confidence that Democrats’ social-spending and climate legislation would pass.

While the president touted G-20 efforts to address climate change, he singled out Russia, China and Saudi Arabia for opposing stronger global climate efforts and standing in the way of a stronger statement on the issue.

G-20 leaders issued a communiqué at the end of the summit that some analysts criticized as too weak. The leaders agreed to stop financing new coal-fired power plants overseas but otherwise hammered out few specifics on how to limit a rise in global temperatures or a timeline for doing so.

China and Russia, Mr. Biden said, “basically didn’t show up in terms of any commitments to deal with climate change,” adding that he was disappointed, but offering no specifics about what measures the countries objected to.

“I think you’re going to see we made significant progress and more has to be done, but it’s going to require us to continue to focus on what China’s not doing, what Russia’s not doing and what Saudi Arabia is not doing,” he said during a news conference on Sunday following the G-20 meeting with world leaders, which focused on climate, global health and economic issues.

Secretary of State Antony Blinken met with Chinese Foreign Minister Wang Yi on the sidelines of the G-20 summit in Rome on Sunday.

Photo: POOL/REUTERS

Turning to domestic issues, Mr. Biden said the U.S. doesn’t need punitive policies to compel people and companies to change their behavior when it comes to climate change, instead pointing to tax credits and grants included in the wide-ranging legislation that are meant to encourage a shift to low-carbon energy sources.

“I don’t think you’re going to need any punitive action to get people to step up and do those things,” he said.

Mr. Biden said the social-spending package Democrats are considering, which would include $555 billion in climate-related provisions, will be approved by Congress. “It’s gonna pass, in my view. But we’ll see,” he said.

His comments came after Democrats cut a $150 billion program from his social-spending plan that would have pushed utilities to draw more power from clean-energy sources. The program, which faced opposition from moderate Democrat Sen. Joe Manchin (W.Va.), would have provided grants to utilities that increase the amount of clean electricity they generate by at least 4% a year, while penalizing utilities that don’t meet that standard.

Mr. Biden has pledged that the U.S. will cut its greenhouse-gas emissions 50-52% below 2005 levels by 2030. Outside analysts said Mr. Biden can meet that target through a mix of executive branch, state and legislative actions on par with what is proposed in the social-spending bill.

The president defended his push to pressure the Organization of the Petroleum Exporting Countries and its partners to increase oil supply even as he was set to travel to the climate summit in Glasgow.

On the surface, the two efforts seem inconsistent, he acknowledged. But he added that the U.S. will continue to rely on fossil fuels in the short-term, even as it seeks to transition toward renewables.

“The idea that we’re not going to need gasoline for automobiles is just not realistic,” he said of the near-term need for oil.

The president suggested he was weighing a response if OPEC doesn’t pump more oil, but declined to discuss it. “What we’re considering doing with that I’m reluctant to say before I have to do it,” he said.

President Biden is set to attend the COP26 climate summit in Glasgow.

Photo: Emily Macinnes/Bloomberg News

Mr. Biden said he was welcomed by world leaders at the G-20 summit following

Donald Trump’s presidency. “We got significant support here,” he said.

He also dismissed polls showing his approval rating is low.

“The polls are going to go up and down, and up and down. They were high early, then they got medium, then they went back up and now they’re low. Look at every other president, the same thing has happened,” Mr. Biden said. “But that’s not why I ran. I didn’t run to determine how well I’m going to do in the polls. I ran to make sure that I would follow through on what I said I would do as president of the United States.”

Earlier Sunday during a G-20 event on supply-chain problems, Mr. Biden urged world leaders to make their supply chains more diverse, secure, transparent and sustainable. “We cannot go back to business as usual,” he said.

As part of those efforts, Mr. Biden issued an executive order delegating authority to the Defense Department to release raw materials from the National Defense Stockpile, a network of facilities that maintains strategic stores of rare-earth minerals and other critical materials.

The president said the executive order would “allow us to react and respond more quickly to shortfalls in the industrial base,” calling on other nations to similarly bolster stockpiles that are critical to national security.

Mr. Biden directed Secretary of State Antony Blinken and Commerce Secretary Gina Raimondo to chair a global forum early next year to chart a path forward on the supply-chain problems.

Write to Catherine Lucey at catherine.lucey@wsj.com and Andrew Restuccia at andrew.restuccia@wsj.com