BEIJING (REUTERS, AFP) - Chinese President Xi Jinping told US counterpart Donald Trump on Monday (July 3) that bilateral relations were "affected by some negative factors", state media said following a series of US actions that angered Beijing.

Mr Xi said in a phone call that Sino-US relations "have achieved important results" since the two met at Mr Trump's Florida resort in April, according to broadcaster CCTV.

But Mr Xi was also quoted as saying that relations "have been affected by some negative factors".

On Monday, China's Defence Ministry said that the US has seriously damaged peace and stability in the South China Sea after a US warship sailed near a disputed island in waters claimed by China.

The ministry resolutely opposes the entry of US warships into Chinese territory, it said in a statement on social media. The actions of the US navy seriously damaged the"political atmosphere" around the development of military ties between the two countries, the ministry added.

The destroyer, the USS Stethem, sailed less than 12 nautical miles from tiny Triton Island in the Paracel Islands archipelago, which is claimed by China as well as Taiwan and Vietnam, a US official told Agence France-Presse.

The distance is commonly accepted as constituting the territorial waters of a landmass. The operation, meant to demonstrate freedom of navigation in disputed waters, came just hours before a scheduled phone call between Mr Trump and Mr Xi.

On Sunday (July 2), Beijing said the passage of the warship was a "serious political and military provocation", one that could further strain relations between the superpowers.

In response China dispatched military vessels and fighter planes, Foreign Ministry spokesman Lu Kang said in a statement late on Sunday, according to state news agency Xinhua.

"The Chinese side strongly urges the US side to immediately stop such kind of provocative operations that violate China's sovereignty and threaten China's security," Mr Lu said.

The statement added that Beijing would continue to take all necessary means to defend national sovereignty and security.

It was the second operation of its kind carried out by the US since Mr Trump took office and comes days after his administration took a number of steps that seemed sure to strain US-Chinese relations.

Last Thursday (June 29), Mr Trump authorised a US$1.42 billion (S$1.95 billion) arms sale to Taiwan, which China considers a rebel province.

The same day, the US Treasury Department imposed sanctions on a Chinese bank accused of laundering North Korean cash.

Also on Thursday, the State Department expressed concern about Beijing's respect for freedom in Hong Kong, on the 20th anniversary of Britain ceding the territory back to China.

And two days earlier, the State Department released a report placing China on a list of the world's worst human trafficking offenders.

All those steps added up to a sharp reversal in tone from April, when Mr Xi travelled to Mr Trump's Mar-a-Lago resort in Florida for a first face-to-face meeting that the US President later said had helped build an outstanding relationship.

Further positive signs had followed, including an agreement in May on exporting US beef and natural gas to China. Mr Trump had praised China's efforts to bring pressure on North Korea over its nuclear and missile programmes.

FRUSTRATION OVER NORTH KOREA

But when those efforts failed to produce results - Pyongyang conducted new missile tests in violation of UN Security Council resolutions - the US President made his frustration known.

Those efforts had "not worked out", Mr Trump tweeted on June 20, adding: "At least I know China tried!"

In their phone call on Monday, "both leaders reaffirmed their commitment to a denuclearised Korean Peninsula," the White House said of Trump's call with Xi from his resort property in Bridgewater, New Jersey, where he is spending a long weekend.

"President Trump reiterated his determination to seek more balanced trade relations with America's trading partners," it added.

The reference to trade was an indication the one-time New York businessman may be ready to return to his tougher-talking ways on business with Beijing after holding back in hopes it would put more pressure on Pyongyang.

Trump and Xi discussed the "peace and stability of the Korean peninsula", China's Foreign Ministry said, without elaborating. Ministry spokesman Geng Shuang later told a daily briefing that the United States was "very clear" about China's position on North Korea. Geng did not elaborate on what Xi told Trump about North Korea.

The latest US "freedom of navigation" exercise comes as Beijing continues muscular efforts to cement its claim to nearly all of the South China Sea, parts of which are also claimed by Taiwan and South-east Asian nations including the Philippines, Brunei, Malaysia and Vietnam.

The United Nations says countries can establish the reach of their territorial waters up to a limit of 12 nautical miles.

China has rapidly built reefs in the area into artificial islands capable of hosting military planes.

Freedom of navigation operations are designed to challenge the sovereignty of countries with claims to disputed territory. Washington has challenged annexations of South China Sea islets while advocating for a diplomatic settlement.

On May 25, the USS Dewey guided-missile destroyer sailed less than 12 nautical miles from Mischief Reef - part of the disputed Spratly Islands in the South China Sea, south of the Paracel Islands.