In a rallying cry to his disaster-hit nation Kan voiced confidence that the government could take "firm control" of the crisis at the crippled Fukushima nuclear power plant as Japan battles to avert a radioactive disaster.
"We will overcome this tragedy and recover," he said in a strident televised address. "We will once more rebuild Japan".
The centre-left leader, wearing an emergency services uniform, was speaking one week after the country's worst ever quake struck, wiping out swathes of coastal areas and knocking out key cooling systems on nuclear power plants.
Kan said Japan was still facing "huge difficulties" in tackling the problems at the plant, which has been hit by a series of explosions.
As workers faced massive danger in trying to avert a full meltdown, Kan said that "although we cannot let our guard down, we will take firm control of the situation and we will be able to emerge from this situation."
Seeking to raise spirits, Kan reminded his people of the nation's post-war recovery.
"We are in a situation in which this crisis is truly testing us as a people," he said.
"While we have been called a small island country, we were able to miraculously rebuild after the war. With the power of the people, we will rebuild this country.
"Because of this quake and tsunami, we cannot falter at any cost. We will rebuild Japan again from scratch. We will face this crisis with determination."
Japan's nuclear safety agency on Friday raised the Fukushima crisis level to five from four on the international scale of gravity for atomic accidents, which goes to as high as seven.
The decision by the Nuclear and Industrial Safety Agency (NISA) puts Fukushima on the same level as the 1979 accident at Three Mile Island in Pennsylvania and the worst ever in Japan.