By Christine Kim

SEOUL (Reuters) - 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.

During 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 pointed to the risk that a military conflict could by sparked by "accidental incidents," said Park Wan-ju, a lawmaker and head spokesman of the ruling Democratic Party.

"The president said the United States speaks of military and diplomatic options, but South Korea can't go through war again," said Park.

Tension on the Korean peninsula has risen in recent weeks as North Korea's leader Kim Jong Un and U.S. President Donald Trump exchanged war-like threats and insults over the North's nuclear and missile development program.

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 if China had a plan to respond to an emergency in North Korea, such as securing nuclear and missile sites, Chinese defense ministry spokesman Wu Qian said, "Military means cannot become an option," and urged talks to resolve the issue."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.

China has vowed to uphold U.N. sanctions against North Korea, besides seeking to get stalled talks restarted with Pyongyang.

On Thursday, China's commerce ministry said North Korean firms or joint ventures in China would be shut within 120 days of the latest United Nations Security Council sanctions passed on Sept. 12.

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Overseas Chinese joint ventures with North Korean entities or individuals will also be closed, the ministry said in a statement on its website, without providing a timeframe.

The ministry had issued similar rules after a previous set of U.N. sanctions in August.

Pyongyang conducted its sixth and largest nuclear test on Sept. 3 and has launched dozens of missiles this year as it accelerates a program aimed at eventually targeting 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, the North's main ally, would probably be extremely unhappy if Pyongyang tested a missile or carried out some other act during its Communist Party Congress, held 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 ever and called for the strengthening of South Korea-U.S. defenses to rein in the North.

Expulsion of North Korean diplomats has been among the measures countries have taken against the reclusive state since its latest nuclear test.

Malaysia banned citizens from traveling to North Korea, citing the escalating tension on the Korean peninsula.

ROTATIONAL DEPLOYMENT

South Korean lawmakers said Chung had told them the United States and South Korea had agreed on the rotational deployment of U.S. strategic assets to South Korea, possibly as soon as year-end. The nature of the assets 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 opposed the deployment of U.S. Terminal High Altitude Area Defence (THAAD) system in South Korea, but rapid improvement in North Korea's missile capabilities prompted the decision.

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.

(Additional reporting by Christian Shepherd and Ben Blanchard in BEIJING; Editing by Simon Cameron-Moore and Clarence Fernandez)