Japan has denied its decision to issue drilling rights in a disputed area of the East China Sea is related to a feud with China over history textbooks.
Both countries have claims over East China Sea deposits
Prime Minister Junichiro Koizumi has said the aim of the drilling is to "turn a sea of confrontation into a sea of co-operation".
China described the exploration for gas and oil in the area as a "provocation".
China has seen violent protests against new Japanese textbooks which it says play down Japan's wartime brutality.
Chinese protests have also been directed at Tokyo's bid for a permanent UN Security Council seat.
China and Japan increasingly competing for natural resources
Have never agreed a maritime border
Also dispute ownership of Senkaku/Diaoyu islands
Senior diplomats from Japan and China are reported to have met in the Chinese capital, Beijing, on Thursday.
The Japanese news agency, Kyodo, said the Chinese side gave security assurances regarding the visit by Japan's foreign minister, Nobutaka Machimura, to Beijing on Sunday.
Last Saturday, a 10,000-strong gathering marched in Beijing to voice their anger at the textbooks - the city's biggest protest since 1999.
Japan's Mr Machimura has said he may propose a joint study on interpretations of their shared history.
Japan has already begun processing applications from companies which want to explore the disputed area of the East China Sea.
Both China and Japan claim the area as lying within their exclusive economic zone (EEZ).
Japanese companies have been waiting for 40 years to be given the go-ahead to drill in the area, which has a potentially vast reserve of natural gas and oil.
"Japan has come up with a provocation to China's right and the norm of international relations," foreign ministry spokesman Qin Gang was quoted by Xinhua news agency as saying.
He said China "will retain the right to make further reaction".
China and Japan are heavily dependent on imported energy, and both are seeking new sources of energy to power their economies.