BEIJING/HONG KONG: China may respond to the U.S. shooting down its suspected spy balloon after warning of "serious repercussions", but analysts say any move will likely be finely calibrated to keep from worsening ties that both sides have been seeking to repair.

Regional analysts and diplomats are closely watching China's response after a U.S. fighter jet shot down the balloon - which Beijing says was an errant weather-monitoring craft - in the Atlantic off South Carolina on Saturday.

China on Sunday condemned the attack as an "over-reaction", saying it reserved the right to use the necessary means to deal with "similar situations", without elaborating.

Some analysts said they will be scrutinising the seas and skies of East Asia for signs of tension, given growing deployments of ships and aircraft from China and from the United States and its allies.

But while bilateral tension has risen in the past few days over the balloon incident, Beijing and Washington have been seeking to improve ties.

The discovery of the balloon in the upper atmosphere above North America prompted the United States to postpone a visit to Beijing this week by Secretary of State Antony Blinken. That trip had resulted from a November summit between Presidents Joe Biden and Xi Jinping.

Both sides are widely seen as keen to stabilise relations after a turbulent few years, with the Biden administration leery of tensions descending into conflict and Xi eyeing a recovery for the world's second-largest economy after a severe COVID-19 slump.

The path of rebuilding U.S.-China relations likely remains on track, said Zhao Tong, a senior fellow at the China office of the Carnegie Endowment for International Peace and a visiting researcher at Princeton University.

"The two sides still have a shared strong interest in stabilising and responsibly managing the bilateral relationship," Zhao told Reuters.

SWEEP UNDER RUG

Collin Koh, a security fellow at Singapore's S. Rajaratnam School of International Studies, predicted China would continue to respond vigorously to U.S. military reconnaissance patrols but stop short of confrontation.

Even in calmer moments, Chinese forces actively shadow U.S. military patrols, particularly at sea, amid tensions over Taiwan and the disputed South China Sea, say regional military attaches.

"Against manned platforms we might expect China to exercise restraint, but against unmanned ones it becomes more uncertain - especially if Beijing believes that it's possible to contain fallout since it involves no crew," Koh said.

He noted China's seizure of a U.S. underwater glider deployed by an oceanographic research ship off the Philippines in December 2016. The Chinese navy later returned it to a U.S. warship.

Christopher Twomey, a security scholar at the U.S. Naval Postgraduate School in California, said any Chinese response would be limited.

"I'd expect they'd protest moderately but hope to sweep this under the rug and reinstate progress on senior-level visits within months," Twomey said, speaking in a private capacity.

Zhu Feng, executive dean of the School of International Studies at Nanjing University, said U.S. officials should stop "hyping" events to ensure a smooth return to the normalised communications they earlier requested from Beijing.

Zhu expressed hope "the two governments can turn the page as soon as possible so that Sino-U.S. relations can return to an institutionalised channel of communication and dialogue".

Some analysts are watching Chinese state media and online activity for hints at any clamour for a tougher response, as China's mainstream state media have stuck to reporting official statements.

On China's heavily censored social media, there was little evidence that nationalistic anger was being stirred up over the incident, with many netizens asking what the fuss was over one balloon.

"Now, China can retire its satellites!," one user joked.