Both sets of military manoeuvres are being held as an Asian economic forum gets underway on the Chinese island of Hainan, which borders the disputed South China Sea.
Almost 90 per cent of the South China Sea has been declared sovereign territory by Beijing under its arbitrary "Nine Dash Line" which extends some 2000km from its mainland. This is despite an international court of arbitration rejecting its ambitious claims in 2016. Vietnam, The Philippines, Malaysia and Brunei are among the nations asserting territorial claims over the sea based on UN conventions.
The convergence also comes as tensions rise between Beijing and Washington over a looming trade tariff "war".
CHINA PUTS CARRIERS TO THE TEST
Chinese media reports this is the first time their refurbished Soviet-era aircraft carrier, Liaoning, has engaged in large-scale live-fire drills.
Satellite photographs released last week showed the ship taking part in an enormous procession of more than 40 warships and submarines off Hainan Island.
While that event was no doubt staged for the cameras, this week's military exercise will pit the best China has to offer against itself.
Hainan Province maritime authorities have banned ship and air activities near the island from today until next Wednesday as the live-fire weapons tests take place.
"This will test the Liaoning's real combat strength as well as joint-operations skills between the aircraft carrier and warships from other fleets," Beijing naval analyst Li Jie is reported as saying.
Beijing's defence ministry spokesman Ren Guoqiang called the large-scale naval drills "routine". This comes just weeks after it announced such "routine" drills would now be conducted in the South China Sea on a monthly basis.
It comes even as China's first homegrown aircraft carrier, an as-yet unnamed upgraded version of Liaoning, is set to go to sea for the first time.
State-run media says it will undergo sea trials within weeks.
At least one other carrier is currently under construction.
MUSCLE ON THE MOVE
Washington currently has three aircraft carrier strike groups currently in or around the South China Sea.
The USS Theodore Roosevelt group arrived in Singapore on Monday after a deployment in the Middle East.
It is likely to conduct drills with two US 7th Fleet carrier groups — centred on the USS Ronald Reagan and USS Carl Vinson — as it passes through the disputed waterways.
The USS Carl Vinson has completed a port call to Vietnam — the first such visit since the end of the Vietnam War in the 1970s. It has been conducting joint exercises with Japanese forces in the Western Pacific, and is believed due to return to the US port of San Diego.
The USS Ronald Reagan group, including the guided-missile cruiser USS Bunker Hill and the guided-missile destroyer USS Sampson is also believed to active in the area.
Elsewhere in the West Pacific, the Amphibious Assault Ship USS Essex is currently at sea undertaking the first operational deployment with the controversial F-35B stealth fighter.
"The US' increasing military presence in the South China Sea indicates that Washington sees Beijing as a serious competitor, not only economically, but also militarily," Zhou said.
"But China realises that the military gap with the US is still very big, and all its military deployments in the South China Sea are basically defensive, including its DF-21D anti-ship (carrier killer) ballistic missile."
