In recent months, President Biden has spent hours speaking with Indian Prime Minister Narendra Modi, South African President Cyril Ramaphosa, and other foreign leaders who have not always supported the Western coalition in support of Ukraine, urging them to stand firm against Russian President Vladimir Putin.

So, the White House was pleasantly surprised when Modi confronted Putin at a summit last month, lecturing him that “today’s era is not of war” and that Putin should “move onto a path of peace,” comments unusual for a leader who has gone to great lengths to remain neutral in the Russia-Ukraine conflict, according to a senior White House official who spoke on the condition of anonymity to discuss private conversations.

As evidenced by these discussions, Biden is now working hard to maintain what has become a central mission of his presidency: the global and domestic coalition supporting Ukraine. As the war enters its first winter, which is likely to be bitter and brutal, some US allies face economic headwinds exacerbated by the conflict, while some Republicans at home express skepticism about the billions of dollars in aid going to Ukraine.

These efforts will be put to the ultimate test on Wednesday, when the United Nations votes on a draft resolution condemning Russia’s annexation of four Ukrainian regions. Biden and other US officials have been working to persuade nonaligned countries in Latin America, Asia, and Africa to abandon neutrality and condemn the Kremlin outright, an effort that analysts say could be bolstered by Russia’s barrage of missile attacks on Kyiv and other major Ukrainian cities on Monday.

According to several senior administration officials, the US hopes that at least 100 of the 193 U.N. member states — the number that supported a 2014 U.N. resolution condemning Russia’s annexation of Crimea — will support the draft resolution. When the United States first proposed a U.N. resolution condemning Russia’s invasion in March, it received support from 141 member states; fewer votes than that, arguably, means diplomatic ground has been lost.

According to a White House schedule, Biden and the Group of Seven leaders will hold a virtual meeting Tuesday morning “to discuss their unwavering commitment to support Ukraine and hold Putin accountable in the face of Russia’s aggression and atrocities,” including Monday’s missile strikes. At the start of the meeting, Ukrainian President Volodymyr Zelensky will join the leaders.

Despite Modi’s surprise confrontation with Putin, some US officials privately admit that they are skeptical of a breakthrough with India, which has extensive political and military ties with Russia. They are optimistic, however, that Putin’s missile barrage on Monday will persuade South Africa and other countries.

Diplomacy, on the other hand, has not been easy. Rising fuel prices and a global food shortage caused by war have disproportionately harmed developing countries in Africa, South America, and Southeast Asia. In meetings with his counterparts, Biden has gone to great lengths to argue that Russian aggression and blockades, not US sanctions, are to blame for their difficulties, according to officials.

Recent events have only reinforced the impression that the war will be a long one. Following the spectacular destruction of a key strategic Russian bridge on Saturday, which Putin blamed on Ukraine, Moscow launched a furious counterattack on Kyiv and other Ukrainian cities on Monday.

Even before that, fighting had erupted on both sides in recent weeks. The fighting is expected to slow during the Ukrainian winter, when cold weather and muddy conditions will stymie military operations. However, with both Ukraine and Russia seemingly convinced that they can and must win, negotiations appear to be a long way off, especially given Putin’s annexation and recent mobilization of up to 300,000 reservists.

So far, the White House has been able to maintain bipartisan support for several multibillion-dollar aid and weapons packages destined for Ukraine, but some Republicans aligned with former President Donald Trump have begun to question why the US is spending so much money on a distant war overseas. And a decision last week by a Saudi-Russian-led coalition to cut oil production is likely to send gas prices back up, further sour the public mood.