Montana's senior U.S. senator, Democrat Max Baucus, on Tuesday filed to run for his sixth consecutive term, saying there's still much work to do to improve the lives of Montanans.

At a news conference in the state Capitol, Baucus said he's eager to use his position as chairman of the powerful Senate Finance Committee to help make health insurance available to all, tackle global warming and bring more jobs to the state.

"I have 900,000 of the world's best bosses," he said, referring to Montana citizens. "We've done an awful lot, but there's still more to do. If Montanans renew my contract, we'll keep doing what's right for Montana."

Baucus, 66, is a heavy favorite to win re-election. He had $6.4 million in his campaign fund as of Dec. 31, and his potential Republican challengers are largely unknown and, so far, under-funded.

State Rep. Michael Lange and industrial facility designer Kirk Bushman, both of Billings, say they're vying for the Republican nomination to challenge Baucus, and each had a few thousand dollars in their campaign accounts at the end of 2007.

However, the only Republican candidate who's paid the filing fee and become an official candidate is Anton Pearson of St. Regis, a political unknown.

Baucus walked into the secretary of state's office Tuesday morning at the state Capitol in Helena and paid his $1,693 filing fee, making his candidacy official.

An attorney who grew up on a ranch north of Helena, Baucus has been a U.S. senator since 1979, winning re-election four times. Before that he served two terms in the U.S. House, representing the old western Montana district.

Baucus declined Tuesday to say anything about his potential opponents this year, but welcomed those who might run against him.

"The more people that run for political office the better," he said. "I only know what I want to do. I pay no attention to any other candidate right now."

Baucus said while he has plenty of issues he plans to work on, from health care to global warming to fighting methamphetamine, he also said Congress may defer substantial action on many issues because it's waiting to see who will be the next president.

On health care, for example, Baucus said he expects the next president to come forth with a "major proposal," so the Finance Committee will hold hearings this year on health-care financing.

"I want to be ready," he said. "We'll be ramping up so we're not just caught flat-footed."

Baucus said he wants to work toward "universal health coverage," as well as control costs, and that he plans to introduce a bill this year that would set up a public-private organization to compare the effectiveness of certain drugs, medical equipment and medical procedures.

"I think that will go a long way toward reducing excessive costs," he said. "We must reduce costs. There is just a lot of wasted dollars in the American system."

Baucus also said he'd like U.S. troops to leave Iraq "as expeditiously as possible," and that while America will continue to have a presence in the Middle East, it shouldn't have bases or active troops permanently in Iraq.

"We can't stay there indefinitely," he said.

Baucus said he favors a cap-and-trade system to reduce carbon-dioxide emissions, as opposed to a carbon tax on energy producers, and that his committee also will examine whether to extend tax cuts supported by President Bush past 2010.

He said he favors extending tax cuts for moderate-income earners, but hasn't decided on the cuts for other income brackets.

Baucus also brushed aside questions about which Democratic presidential candidate he plans to support this year, suggesting he might first want to see how Democrats in Montana vote in the June 3 primary election.

Baucus is one of the state's "superdelegates" and has a vote at the Democratic National Convention this summer on the nominee for president.

Baucus bio

Name: Max Baucus.

Office sought: U.S. senator.

Political party: Democrat.

Office salary: $169,300.

Age: 66.

Birth date and place: Dec. 11, 1941, in Helena.

Home: Helena.

Occupation: U.S. senator and attorney.

Family: Wife, Wanda, one son from previous marriage.

Education: Helena High School graduate, 1959; bachelor's degree in economics from Stanford University, 1964; law degree, Stanford University, 1967.

Employment prior to political career: 1971-74, attorney in private practice, Missoula; 1971, legal assistant at U.S. Securities and Exchange Commission, Washington, D.C.; 1967-69, staff attorney, U.S. Civil Aeronautics Board, Washington, D.C.

Military: None.

Political experience: 1979-present, U.S. senator representing Montana; 1975-78, U.S. representative for old western Montana district; 1973-74, state representative from Missoula; committee coordinator and executive director of the 1972 Montana Constitutional Convention.