TOKYO - Japan's popular prime minister, Junichiro Koizumi, has taken a gamble that could slice his public support and cloud his future by firing his equally popular foreign minister in an attempt to end a parliamentary standoff.

Koizumi late on Tuesday fired controversial Foreign Minister Makiko Tanaka after her latest dispute with top bureaucrats and a ruling party heavyweight delayed enactment of a public spending package and threatened to sidetrack his economic reforms.

Koizumi also asked the Foreign Ministry's top bureaucrat to resign and Muneo Suzuki, a ruling party lawmaker involved in the dispute, to step down from his influential parliamentary post.

The prime minister's aloofness while the feud worsened had left him open to charges of dithering. But his attempt to appear both decisive and even-handed might not win much public applause.

"I think it's very risky," said Gerald Curtis, a professor at Columbia University in New York and an expert in Japanese politics. "The woman is still very popular."

Support from Tanaka -- daughter of the late ruling party kingmaker Kakuei Tanaka -- helped Koizumi defeat Liberal Democratic Party (LDP) rivals in a leadership race last April.

But the outspoken Tanaka quickly became a thorn in Koizumi's side because of her battle with bureaucrats at her ministry, tainted by scandals over the misuse of public funds, and with one of Koizumi's closest aides, Chief Cabinet Secretary Yasuo Fukuda.

Koizumi's popularity is still sky-high after nine months in office, but stems largely from his promises to root out the vested-interest politics which kept the LDP from adapting to a changing economic landscape and carrying out reforms.

Though a long-time member of a powerful LDP faction, Koizumi is a party maverick and public support is almost his only weapon against anti-reform rivals in his own camp.

That support could evaporate if voters judge he is just an old-style LDP politician with reformist slogans and media savvy.

"Koizumi's support is extremely soft. It can disappear in a minute," said Steven Reed, a political science professor at Chuo University in Tokyo.

The risk is that Koizumi, in his effort to cut through the political tangle delaying economic steps, could end up leaving voters in doubt about his commitment to change.

Tanaka's latest row centred on her allegation that Suzuki, known for his clout with diplomats, had tried to bar certain non-governmental organisations (NGOs) from an international conference on aid for Afghanistan last week in Tokyo.

Suzuki had been seen not only as a patron of those diplomats unhappy with Tanaka's efforts to clean up her ministry -- tainted by scandals over the misuse of public funds -- but as a symbol of the old LDP, where backroom deals and vested interests held sway.

"Right now, Koizumi is looking a lot like the old LDP," said Chuo University's Reed. "If there's a problem, get rid of it rather than fixing it. There is not a word about truth and justice, just 'we're worried about getting bills passed'."

Voters have veered between distaste for Tanaka's heavy-handed ways and diplomatic faux pas, and support for her battle to put bureaucrats and their political backers in their place.

On Wednesday, the conservative Yomiuri newspaper said it was time for Tanaka to go.

"The bickering...has created a chasm between the minister and bureaucrats that will be difficult to bridge," the paper said in an editorial apparently written before she was fired.

Public opinion, however, had appeared to be swinging behind the foreign minister in the latest feud.

"Even people who thought that she was a terrible foreign minister believed that, on this issue, she was on the right side," Curtis said. "It was the wrong issue at the wrong time."

Opposition party leaders vowed to pursue the facts behind the dispute and on Wednesday again grilled Koizumi over the affair at an Upper House budget committee.

Koizumi, who thus far has excelled at reading which way public opinion was blowing, could keep his standing with voters if he finds a credible replacement for Tanaka, analysts said.

Among the names floated by media was Sadako Ogata, Japan's highly respected special envoy for Afghan affairs who co-chaired last week's aid conference, though analysts questioned whether Ogata, a former U.N. high commissioner for refugees who reportedly turned down the post last April, would take the job.

Some critics said that while Suzuki had received a slap on the wrist, Koizumi's move would merely serve to embolden LDP forces opposed to his reforms and dampen prospects for change.

"His popularity will decline and the rivals will unwind his policies," said UBS Warburg political analyst Shigenori Okazaki.

"If it falls below 50 percent, they can get rid of him. If it stays above 50 percent, they can just keep him around as decoration." Nampa-Reuters