The leaders of India and the United States vowed Tuesday to ratify the Paris climate accord this year, pledged to nail down terms for limiting a potent greenhouse gas used as a refrigerant in air conditioners, and set a one-year deadline for concluding a deal for six commercial nuclear power plants.

But the two sides provided few specifics about how they would achieve those goals beyond saying that President Obama and Prime Minister Narendra Modi, who were meeting at the White House, share the same objectives and have established time frames for resolving differences.

Even without the agreed deadlines, the recent pledge by presumptive Republican presidential nominee Donald Trump to renegotiate the Paris climate accord if he is elected has added a sense of urgency among world leaders to make sure the pact goes into effect before the end of the year. Thirty days after at least 55 countries accounting for at least 55 percent of global emissions have moved to join the agreement, the Paris accord enters into force.

India accounts for 4.1 percent of global emissions. “If India joins, it will practically put us over the hump of 55 percent of global emissions required for ratification,” said Andrew Light, a former State Department negotiator who is now at the World Resources Institute.

[Here are three climate change breakthroughs possible during Modi’s trip to Washington]

India is a key country for the United States, given tensions with Pakistan and India’s status as a bulwark against China in South Asia. But Obama has put climate and energy issues at the forefront of relations with Modi.

The focus among negotiators leading up to Tuesday’s meeting was an effort to work out details for restricting hydrofluorocarbons, or HFCs, by adding them to the Montreal Protocol, the global treaty adopted in 1987 to address ozone depletion.

The two nations agreed to link increased financial support for India from a multilateral fund with what Obama adviser Brian Deese called “an ambitious approach to phase out HFCs altogether.”

Without an agreement, the use of HFCs is expected to soar as the growth of the middle class in India fuels an increase in the sale of air conditioning and refrigerators. India is the world’s third-largest carbon emitter, and HFCs have a global warming power thousands of times greater that carbon dioxide.

India has been pressing for a longer “grace period” before starting to phase out HFCs and a longer phase-out period. But the United States has been urging action before the HFC industry grows. “For India, it doesn’t make sense to build an industry that is a generation behind. And then it doesn’t make sense for us to pay to dismantle it,” said David Doniger, director of the climate and clean air program at the Natural Resources Defense Council.

[Greenhouse gas emissions from this surprising source could doom the Paris climate accord goal]

The Montreal Protocol is one part of a broad effort by Obama to convince Modi to act to prevent an explosion of greenhouse gas emissions as India’s economy speeds ahead. Obama and Modi were also expected to discuss Tuesday how India can reach its 100 gigawatt target for solar power by 2022. The leaders backed the creation of two mechanisms to help stimulate the scores of billions of dollars of financing that will be needed.

One mechanism will be a joint $40 million program to provide high-risk capital for areas off the grid in India, where about 240 million people have no access to electricity. The second mechanism is a joint $20 million India Clean Energy Finance Initiative. This will help developers put together renewable projects and then get substantial financing with the help of the Overseas Private Investment Corp. OPIC, a U.S. government agency, provides loan guarantees and political risk insurance to American firms investing overseas.

Deese estimated that the two mechanisms together could catalyze up to $1 billion in investment — still a small fraction of the financing India will need to meet its goal.

On the nuclear power front, Westinghouse Electric (now owned by Toshiba) has been negotiating with India in the hopes of selling it six AP-1000 nuclear reactors. The project site was recently moved to the southern state of Andhra Pradesh, where site preparation is underway. ­Local opposition prevented the multibillion-dollar project from moving ahead in Modi’s home state of Gujarat.

Nisha Desai Biswal, assistant secretary of state for South Asian affairs, told a Senate committee on May 24 that a commercial deal was “quite close.”

[The impressively awkward hugs and handshakes of India’s Narendra Modi]

The stumbling block has been an article in a 2010 Indian law that would make Westinghouse — and its suppliers — potentially vulnerable to crippling litigation under local Indian laws in the event of an accident. India has offered to establish insurance pools, but companies have not accepted that plan. There was no indication Tuesday that the issue had been resolved.

“They’ve painted themselves into a corner,” Omer F. Brown, a lawyer and nuclear liability expert, said of the Indian government. “I don’t know how they get out of it, given that they wrote the law the way they did.”

Westinghouse and General Electric’s nuclear arm have been striving to reach a deal with India for more than a decade, and in 2008 Congress approved an agreement to promote nuclear cooperation with India, which critics said undermined half a century of U.S. nonproliferation efforts.

Energy and climate issues have overshadowed other aspects of U.S.-India relations. Non-proliferation groups have raised questions about the Obama administration’s current efforts to persuade the Nuclear Supplier Group, which deals with the export of nuclear materials and equipment, to accept India as a member. So far, membership in the NSG has required that a state be a member of the Nuclear Non-Proliferation Treaty. But India chose not to sign the treaty in 1968 and later built its own nuclear weapons, which it tested in 1974 and again in May 1998.

Daryl Kimball, director of the Arms Control Association, said the U.S. push for India’s membership in the NSG “would compound the damage in my view of the Bush administration’s exemption” for India. He and 16 other non-proliferation experts, including some from the Obama administration, have written a letter urging the administration to drop its support for India’s membership.

Human rights groups have also complained that Obama has failed to challenge Modi over women’s rights, the treatment of independent domestic critics and encouragement of Hindu nationalism. John Sifton, the Asia advocacy director of Human Rights Watch, noted that the government recently revoked the non-governmental organization status of the Lawyers’ Collective, a well-regarded advocacy group that promotes legal reforms.