New Congress convenes, focused on recession (Reuters) - Democrats celebrated their increased clout in the U.S. Congress on Tuesday, swearing in new members who are expected to help President-elect Barack Obama enact a massive economic stimulus package.

Gavels sounded at about noon EST (1700 GMT), opening the Senate and House of Representatives a day after Obama visited the Capitol to press Republicans as well as fellow Democrats for quick action on a $775 billion package of tax cuts and new spending to stem a deepening recession.

Obama takes office on January 20, which would give Democrats control of the White House and Congress for the first time in 14 years.

"We need action, and we need action now," Nancy Pelosi, a California Democrat, declared after colleagues elected her to a second term as House speaker.

Despite such challenges as the ailing economy, two wars and an estimated 46 million Americans without health insurance, the opening day of Congress amounted to somewhat of a victory party for the Democrats who expanded their control of the Senate and House in the November election.

"We are grateful to begin anew with a far more robust Democratic majority," said Senate Majority Leader Harry Reid.

Reid hailed Democrats' expanded majority, but echoed Obama's call for "change in Washington" after years of partisan bickering and gridlock.

"I say to my Republican colleagues: With American troops fighting two wars overseas, we are in this together," Reid said. "With the American people suffering a staggering economic crisis here at home, we are in this together."

The Democratic celebration in the opening of Congress was muted somewhat by a flap over a pair of seats that remained empty in the 100-member Senate.

TWO EMPTY SEATS

As lawmakers and family members partied, Democrat Roland Burris of Illinois, selected to fill the Senate seat vacated by Obama, was denied entrance.

The Illinois secretary of state refused to certify his appointment by scandal-plagued Illinois Gov. Rod Blagojevich, who had earlier been arrested and accused of attempting to sell the seat which had formerly been occupied by Obama.

Senate Democrats opposed the governor's action as tainted. The matter of certification is now in court in Illinois.

On a related front, Reid yielded to Republican pressure and put off an effort to seat comic-turned-politician Al Franken of Minnesota, also a Democrat. He faces legal challenges of his razor-thin election victory.

If both had been sworn in, the Democrats' majority in the 100-member Senate would swell to 59 -- their biggest margin in 30 years and just one short of the needed 60 votes to overcome Republican roadblocks.

But with the possibility of court battles, back-room negotiations and procedural wrangling, it could take months to fill the two seats.

Democrats controlled Congress the past two years, but Senate Republicans blocked much of their agenda. With an increased Senate majority and the help of some moderate Republicans, Democrats hope to pass much of the previously stalled legislation.

In the 435-member House, there are 256 Democrats, up from 235 in the last Congress. There is one vacancy, the seat Illinois' Rahm Emanuel left to become Obama's chief of staff.

While the economic stimulus package is the first priority in Congress, there are scores of others.

Democrats aim to withdraw American troops from Iraq and redeploy many of them to the war in Afghanistan, expand health care, bolster regulation of the troubled financial services industry and develop alternative energy sources while curbing pollution that contributes to global warming.

Senate Republican Leader Mitch McConnell vowed to cooperate when possible, but also made it clear there could be clashes, starting with Obama's economic recovery plan.

"We should encourage, not discourage questions about this bill in a reckless rush to meet an arbitrary deadline," McConnell said in a prepared statement.

House Republican Leader John Boehner said, "President-elect Obama has expressed a desire to govern from the center and put the needs of our country first."

"Washington is a difficult town, and it won't always be easy for him to do these things. But when our new president extends his hand across the aisle to do what is right for our country, Republicans will extend ours in return," Boehner said.

(Additional reporting by Susan Cornwell and Jeremy Pelofsky; editing by David Wiessler)

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