Chinese President Xi Jinping expressed his sincere gratitude to Bill and Melinda Gates for their foundation’s support to China after the outbreak of the novel coronavirus.

Xi thanked the foundation for its “generous support” provided at a critical juncture, in a letter to Bill Gates posted by the official Xinhua news agency.

Xi complimented the foundation’s early efforts in the global cause of fighting against the virus and said he was grateful for a letter from Gates expressing support for the Chinese people.

“Unity and cooperation is the most powerful weapon” in the battle against the virus, Xi said in the letter, indicating his support for the Gates Foundation’s coordination with Chinese agencies on the ground.

The foundation earlier this month raised its commitment to provide up to $100 million for the global response to the outbreak. The foundation said that part of the donation will be used to acceleration the detection, isolation and treatment of the coronavirus in China and other countries that have confirmed cases.