Taro Aso said in his first news conference after being elected Wednesday that he would do what it takes to shield the Japanese economy from the financial meltdown in the United States.
Aso has not disclosed any details and limited himself to saying that the moves would aim to support working people and small- and medium-sized companies.
Japan's economic growth stalled this year, and inflation is increasing.
Aso, an outspoken conservative, took power after overcoming opposition forces in the split parliament, tasked with rejuvenating the ailing ruling party ahead of elections.
Aso, 68, was chosen as president of the long-ruling Liberal Democratic Party on Monday, and already had begun piecing together a Cabinet expected to include a fellow hawk as finance chief.
The former Olympic sharpshooter was declared premier after the LDP-controlled lower house overruled the upper house, which had voted for Ichiro Ozawa, the chief of the opposition Democratic Party of Japan.
Aso, known for his rightist leanings and acerbic wisecracks, will lead a country wracked by political divisions and spiking concerns over the economy, which has stalled amid the ballooning financial crisis in the United States.
"If you look at the current period, it's not a stable one," he told reporters on Wednesday morning. "These are turbulent times with the financial situation and everything else."
The first task for Aso, who takes over from Yasuo Fukuda after a rocky one year in office, will be to put together a Cabinet capable enough to raise public support ahead of lower house elections that could come before the end of the year.
The initial choices, however, included many of the ruling party operatives who have circulated through previous Cabinets.
Shoichi Nakagawa, a former economic minister considered to be in the right-wing of the LDP, was seen as the leading candidate to become the new minister of finance.
Two years ago, Aso and Nakagawa caused a stir by suggesting Japan - whose pacifist constitution foreswears war - should have a debate on whether to acquire nuclear weapons. At the same time, Nakagawa called the U.S. atomic attack on Nagasaki "a crime."
Kaoru Yosano, who lost to Aso in the LDP presidential race, was expected to keep his post in charge of economic and fiscal policy.
It was unclear how Aso would square his stated policy of using government spending to buoy the economy with Yosano's overriding concerns about the country's burgeoning budget deficit. Aso has said he would refuse to raise the 5 percent consumption tax for at least the next three years.
Former Defense Minister Shigeru Ishiba was widely reported to be Aso's choice for agriculture minister. Fukuda's farm chief recently stepped down amid a spiraling scandal over pesticide-tainted rice. Hirofumi Nakasone, the son of 1980s nationalist Prime Minister Yasuhiro Nakasone, was to be foreign minister.
Jiro Yamaguchi, political scientist at Hokkaido University, said the Cabinet picks reflected Aso's focus on keeping the LDP in power.
"The lineup clearly shows that Aso only cares about the approaching elections, not policies," Yamaguchi said. "But rather than sending a clear message to voters, the lineup largely included people with close ties with Aso."
Aso, Japan's first Catholic leader, will soon have to decide whether to call early elections for the lower house to prove his party - which has governed for nearly all the past 53 years - still has a mandate to rule.
Such an election would be a major gamble for the party, which is bleeding public support and suffering widespread anger over mismanagement of pension funds and a general dissatisfaction with the status quo.
Elections can be called by the prime minister at any time, but must be held by next September.
Opposition leaders immediately attacked the new government.
"Aso is on the opposite end of the spectrum from regular people, who are making ends meet and face difficulties in their daily lives," said Social Democratic Party leader Mizuho Fukushima. "He is totally ignoring them and doing his own politics."
Aso has also said that he will continue to place relations with Washington as Japan's top diplomatic priority, while trying to improve ties with neighboring China, whose growing economic and military clout Aso once described as a "major threat."
Aso, the scion of a political family from southern Japan, could face trouble if he continues his record of ruffling feathers at home and abroad with caustic off-the-cuff comments.
He recently drew ire, for instance, by comparing the top opposition party to the Nazis. In 2001, he was forced to apologize after saying the ideal country would be one that attracts "the richest Jewish people."