The presidents of Russia and Iran, facing increased domestic pressure from drawn-out wars, were set to rally with the leaders of China and India at a summit on Monday in Central Asia.

President Vladimir V. Putin of Russia and President Masoud Pezeshkian of Iran headed to Bishkek, the capital of Kyrgyzstan, for a two-day meeting of the 10-nation political and security grouping known as the Shanghai Cooperation Organization. The forum will allow Russia and Iran to demonstrate alternative sources of support as they work to defy Western efforts to isolate them.

Though it once counted only Russia, China and four Central Asian nations as members, the grouping expanded in 2017 to include India and Pakistan and more recently to add Belarus and Iran. In the process, it has become a growing counterpoint to Western-led political and security groupings.

At the center of the proceedings is the most powerful leader in attendance, President Xi Jinping of China. No nation has been more critical to Russia and Iran in sustaining their economies and war efforts than China. Mr. Xi has undermined efforts by the United States and its allies to pressure Russia and Iran economically, employing Beijing’s vast geopolitical and economic clout as the world’s largest importer of crude oil and exporter of consumer goods.

The wars have helped increase China’s already rising power. Mr. Xi’s biggest rival, the United States, has been distracted by the war in Iran and has pulled out some of its military forces from Asia and Europe. Last month, Mr. Xi was able to brush off threats by President Trump that the United States would inflict an “economic D-Day” on countries that provided Tehran a lifeline.

This week’s summit is a reminder of the limits of U.S.-led economic warfare. Both Russia and Iran have managed to maintain critical alliances outside the West that have come in handy at different stages of their conflicts. The two nations have managed to handle domestic fallout from the wars for longer than some Western officials had expected.