The Group of Seven summit is due to open in the remote southwestern British county of Cornwall on Friday. It will be the first in-person G7 summit in two years.
The leaders will discuss how coronavirus vaccines should be fairly distributed to bring the COVID-19 pandemic under control around the world.
They will also talk about climate change. The UN climate change conference known as COP26 will take place in Britain this autumn.
US President Joe Biden is participating in the summit for the first time. Under his predecessor Donald Trump, the G7 showed signs of discord as Trump pushed his "America First" policy.
Biden wants to restore solidarity with the other leaders by promoting cooperation with countries that share values with the United States.
In May, G7 foreign ministers jointly expressed serious concern about the situation in and around the East and South China seas, where Beijing is increasing its presence, and about human rights in Xinjiang and Tibet.
The US government says Biden and other leaders plan to announce a new program to provide infrastructure financing to developing countries as a counterweight to China's Belt and Road initiative.
Observers are closely watching whether the leaders will be able to adopt a united stance toward China, as there are differences among them.
The three-day summit will close on Sunday. The leaders are scheduled to release a joint declaration.