China has rejected an American accusation that five of its ships harassed a US navy surveillance vessel in international waters in the South China Sea.
The Chinese Foreign Ministry said the American ship had been breaking international and Chinese law.
Our correspondent Quentin Sommerville sent this report from Beijing.
China says a US navy surveillance vessel, the Impeccable, was acting illegally inside Chinese waters.
The country's Foreign Ministry says it has asked the US to immediately stop such incursions which it describes as totally unacceptable.
The Pentagon says five Chinese ships harassed the Impeccable, forced it to a dead stop, and interfered with the sonar equipment.
The ship was in international waters according to the United States.
Climate scientists are beginning a three-day conference in Denmark aimed at updating the accepted thinking on global warming ahead of political talks later this year.
The BBC's environment reporter says this conference will have the very latest data and won't have to agree its every word with politicians.
Our correspondent says this is likely to produce greater clarity and a much higher forecast for sea level rises with dramatic implications for many nations.