Japan's Prime Minister Shinzo Abe has expressed "profound grief" over his country's actions in World War Two.
In a statement marking 70 years since Japan's WW2 surrender, he upheld apologies and expressions of remorse made by past governments, but did not issue a new formal apology of his own.
He added that future generations should not "be predestined to apologise".
Both China and South Korea responded by saying they wanted a more "sincere" response from Tokyo.
They suffered extensively under Japanese wartime occupation, and say Japan has never fully atoned for its actions.
Analysis: Rupert Wingfield-Hayes, BBC News, Tokyo
Mr Abe walked a careful line, maintaining previous apologies, but also saying future generations should not have to go on apologising endlessly.
He did not deviate from the now standard wording of Japan's official apology, but also sought to cast Japan's 20th Century history as anti-colonial.
Japan's defeat of Russia in 1905 had, he said, encouraged many people under colonial rule from Asia to Africa.
He also made it clear he thinks the world cannot continue demanding apologies from Japan forever.
Mr Abe said that Japan had inflicted "immeasurable damage and suffering" on "innocent people" during the war.
"Japan has repeatedly expressed the feelings of deep remorse and heartfelt apology for its actions during the war," he said.
"Such position articulated by the previous cabinets will remain unshakeable into the future," the official translation of his remarks said.
He stressed that Japan's post-war generations, which made up more than 80% of the population, had "nothing to do with that war". But he added that the Japanese still had to "squarely face the history of the past".
Mr Abe is under pressure not only to avoid angering China and South Korea, important regional allies, but also to satisfy domestic nationalists who have grown uneasy with the repeated demands that they apologise for historic decisions.
He did not directly refer to the women, known as comfort women, who were forced to be sex slaves for Japanese soldiers during the war, but said that "the dignity and honour of many women were severely injured during wars in the 20th Century".
China's Vice Foreign Minister Zhang Yesui responded to Mr Abe's speech by telling the Japanese ambassador that Tokyo "should make a clear explanation and a sincere apology" to those who suffered during that period.
He also urged Japan to "take concrete actions to gain the trust of its Asian neighbours and the global community", according to a statement on the foreign ministry website.
Meanwhile, South Korea's foreign minister has called for Japan's "sincere action", Yonhap news agency reports.
Reaction from around the region
BBC's Stephen Evans in South Korea
The main news agency which supplies the country's newspapers with information said: "Abe skips his own apology for Japan's wartime past".
It noted that he had maintained previous expressions of "deep remorse and heartfelt apology" but added that he didn't offer his own apology clearly, even as he expressed "profound regret" for the dead of war.
The tone of the comment is that Prime Minister Abe has not changed his stance - a stance which many South Koreans found unacceptable.
This past week one Korean protester set fire to himself outside the Japanese embassy in Seoul. Mr Abe's speech is unlikely to have defused that kind of street anger.
Vincent Ni, BBC Chinese Service
Abe's speech was one of the most discussed topics on Weibo, China's equivalent to Twitter. Reaction was mixed among the 30,000 plus tweets, but the overwhelming majority seemed to feel that the Japanese PM's speech was "not genuine".
"Does Abe mean Japan is no longer responsible for its war atrocities? Do they no longer have to pay for what they did in the past? Perhaps many young people will think like this, but those comfort women wouldn't agree," wrote one user.
But another was more sympathetic to Japan. "We always hope Japan to do this and that, but why don't we make more efforts ourselves and improve our own country?"
In 1995, then Prime Minister Tomiichi Murayama issued a landmark apology offering a "heartfelt apology" and expressing "deep remorse" for Japan's "colonial rule and aggression".
His sentiments were repeated 10 years later by Prime Minister Junichiro Koizumi.
Mr Abe's speech comes weeks after Japan's lower house approved bills that would change the country's security laws and enable its forces to fight overseas for the first time since WW2.
The prime minister has pushed for the changes, but polls show more than half of Japanese citizens oppose them.