South Korea expects more provocative acts by North Korea next month to coincide with the anniversary of the founding of the North Korean communist party and China's all-important Communist Party Congress.
In a meeting with President Moon Jae-in on Thursday, national security adviser Chung Eui-Yong said he expected Pyongyang to act around Oct. 10 and 18, but gave no details.
The South Korean security adviser's report also noted the risk of that a military conflict could be sparked by "accidental incidents," Park Wan-Ju, a lawmaker and head spokesman of the ruling Democratic Party, said.
"The president said the United States speaks of military and diplomatic options, but South Korea can't go through war again," said Park.
Tensions on the Korean peninsula have escalated in recent weeks as North Korea's leader Kim Jong Un and US President Donald Trump exchanged bellicose threats and insults over the North's nuclear and missile development programme.
The North has accused Trump of declaring war after he warned Kim's regime would not last if he persisted in threatening the United States and its allies, having earlier warned North Korea would be totally destroyed in such an event.
Asked whether China has a plan to respond to an emergency in North Korea, such as securing nuclear and missile sites, Chinese defence ministry spokesman Wu Qian said that "military means cannot become an option" and the issue should be resolved through talks.
"The Chinese military will make all necessary preparations to protect the country's sovereignty and security and regional peace and stability," he added, without elaborating.
Pyongyang conducted its sixth and largest nuclear test on Sept. 3 and has launched dozens of missiles this year as it accelerates a programme aimed at enabling it to target the United States with a nuclear-tipped missile.
The United States and South Korea are technically still at war with North Korea because the 1950-53 Korean conflict ended with a truce and not a peace treaty.
China, North Korea's main ally, would likely be extremely unhappy if Pyongyang tested a missile or carried out some other act during its Communist Party Congress, held once every five years.
Park said President Moon told the meeting that Washington and Seoul agreed that pressure needed to be applied to North Korea, with the door to talks still open.
In a separate speech on Thursday, Moon said cooperation with the international community to curb the North's nuclear ambitions was at its highest level ever and called for the strengthening of South Korea-U.S. defences to rein in the North.
Since the North's latest nuclear test, countries have taken measures against the reclusive state, including the expulsion of North Korean diplomats.
Malaysia said on Thursday all its citizens are banned from travelling to North Korea until further notice due to escalating tensions on the Korean Peninsula.
South Korean lawmakers said Chung had told them that the United States and South Korea had agreed on the rotational deployment of US strategic assets to South Korea, possibly as soon as year-end. What kind of assets would be rotated was not specified.
President Moon added it was inappropriate to discuss the deployment of nuclear weapons in South Korea, the lawmakers said.
Moon said he had personally been against the deployment of US Terminal High Altitude Area Defence (THAAD) system in South Korea, but the decision was made as North Korea's missile capabilities were quickly improving.
China opposes the deployment of THAAD because it believes its powerful radar could be used to look inside its territory. South Korea and the United States have said it is only to curb North Korea's missile threats.