A senior Chinese official says relations with Japan are at their most difficult since diplomatic ties were established more than 30 years ago.
Anti-Japanese protests began two weeks ago
He spoke in the wake of a series of anti-Japan protests in Chinese cities sparked in part by Tokyo's approval of controversial new history textbooks.
Japan's foreign minister has expressed disappointment at China's refusal to apologise for the violent protests.
But his Chinese counterpart says Beijing has nothing to apologise for.
Li Zhaoxing said the real issue was Japan's failure to accept its wartime record.
Chinese protesters are angry about new Japanese school textbooks, which they say gloss over wartime atrocities. They are also opposed to Japan's bid for a permanent seat on the United Nations Security Council.
"There are serious difficulties in the China-Japan relationship and these difficulties are the most serious ones since 1972, when China and Japan normalised relations," China's Vice Foreign Minister Wu Dawei told reporters at a press conference on Monday.
Japanese Foreign Minister Nobutaka Machimura went to Beijing on Sunday hoping to ease tensions. He wanted reassurance from the Chinese government that it would prevent further attacks on Japanese interests.
What he got, says BBC Beijing correspondent Louisa Lim, was a talking to.
Japanese Chief Cabinet Secretary Hiroyuki Hosoda said on Monday that it was "extremely regrettable" there was no apology.
Japanese officials are increasingly concerned about long-term damage to booming trade and investment between the two countries. Tokyo stocks have fallen, with the key Nikkei index down 3% - its biggest one-day loss in 11 months.
Leaders may meet
Tokyo has suggested a further meeting on the issue this week between Japanese Prime Minister Junichiro Koizumi and his Chinese counterpart Hu Jintao on the sidelines of an Asia-Africa summit in Indonesia.
Beijing has yet to decide whether this should go ahead.
Saturday and Sunday saw the third consecutive weekend of anti-Japanese protests in China. There were large demonstrations, involving thousands of people, in Shenzhen and Shanghai, and smaller protests reported in the cities of Shenyang, Zhuhai, Dongguan and south-western Chengdu.
Analysts say the scale of the disturbances is unusual for China, and indicates tacit official support for the protesters.
But our correspondent says Beijing appears to be moving towards controlling activities in certain areas - for example, university students have been told to stay on campus.
The protests were triggered by Japan's decision to approve eight school textbooks which critics say gloss over the country's actions before and during World War II.
Among the issues causing outrage is the description of the Japanese army's massacre of between 50,000 and 300,000 civilians in the Chinese city of Nanjing in 1937 and 1938 as "an incident".
Tokyo says private companies, not the government, were responsible for the texts, and that it is up to individual school districts to decide which books they use.