image copyrightReutersimage captionNato Secretary-General Jens Stoltenberg said the military alliance didn't want a Cold War with China
The head of Nato has urged members to respond to China's rise ahead of a key summit designed to shore up US support for the western alliance.
Nato leaders are expected to issue a statement branding China a security risk after they meet in Belgium on Monday.
Secretary-General Jens Stoltenberg said the summit 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 expansion of the Soviet Union.
In recent years, the alliance has come under strain as leaders have 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 US commitment to defend European partners.
But in contrast, his successor Joe Biden has sought to reassert American backing for the 72-year-old alliance.
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"I want to make it clear: Nato is critically important for US interests," Mr Biden said as he arrived at the summit on Monday.
He said his country had a "sacred obligation" to observe Article 5 of Nato's founding treaty, which commits members to defend each other from attack.
image copyrightReutersimage captionPresident Biden called Nato critically important for US interests
President Biden's national security adviser, Jake Sullivan, said the Nato talks would focus on collective security, including standing up to China and its rapid military rise.
"We're not entering a new Cold War and China is not our adversary, not our enemy," Mr Stoltenberg told reporters at Nato headquarters ahead of the summit.
"But we need to address together, as the alliance, the challenges that the rise of China poses to our security."
Climate change, cyber-security, Russia, and the withdrawal of Nato forces from Afghanistan – the alliance's longest overseas deployment – will also be on the agenda.
Why is Nato focusing on China?
China is one of the world's leading economic and military powers, whose ruling Communist Party has a tight grip on politics, daily life and much of society.
Nato has become increasingly concerned about the growing military capabilities of China, which it sees as a threat to the security and democratic values of its members.
In recent years, the alliance has grown wary of China's activities in Africa, where it has set up army bases, and joint military exercises with Russia.
What is Nato?
- The North Atlantic Treaty Organisation, known as Nato, is the world's most powerful regional defence alliance
- It was set up in 1949, after World War Two, to counter the threat of communist expansion
- It was founded on the principle of collective defence between allies
- It originally had 12 members, but now has 30
- Read more about Nato
media captionNato explained in 80 seconds
On Monday, Mr Stoltenberg said China was "coming closer" to Nato in terms of its economic, military and technological capabilities.
That assessment was echoed by UK Prime Minister Boris Johnson, who said there is a need to manage the challenges posed by China.
"When it comes to China, I don't think anybody around the table wants to descend into a new Cold War with China," Mr Johnson said on arrival at the Nato summit.
Diplomats told Reuters news agency that the Nato summit's final statement – known as a communique – would not call China an adversary. However, it will refer to China as a "systemic" challenge to the security of Nato members, Reuters reported.
"China will feature in the (Nato) communique in a more robust way than we've ever seen before," said Mr Sullivan, President Biden's top security adviser.
Nato's tough message on China followed criticism of the country by the G7, a group of major economies that met for a summit in England last week.
In a communique G7 leaders scolded China over alleged human rights abuses and demanded a transparent investigation of the origins of Covid-19 in the country.
In response, China accused the G7 of "lies, rumours and baseless accusations" in a statement through its embassy in the UK.