The head of Nato has urged members to respond to China's rise at a summit designed to shore up US support for the Western alliance.
The summit is expected to issue a statement describing China's behaviour as a "systemic challenge" after the meeting in Belgium, reports the BBC.
Secretary-General Jens Stoltenberg said the meeting was a "pivotal moment" for the alliance.
It is US President Joe Biden's first Nato meeting since taking office.
Nato is a powerful political and military alliance between 30 European and North American countries. It was established after World War Two in response to the threat of communist expansion.
In recent years, the alliance came under strain as leaders debated its purpose and funding.
Tensions grew during the presidency of Donald Trump, who complained about his country's financial contributions to the alliance and questioned the US commitment to defend European partners.
In contrast, Joe Biden has sought to reassert American backing for the 72-year-old alliance.
"I want to make it clear: Nato is critically important for US interests," Biden said as he arrived at the summit on Monday.
His country, he said, had a "sacred obligation" to observe Article 5 of Nato's founding treaty, which commits members to defend each other from attack.