Washington (CNN) -- Republican Scott Brown was sworn in Thursday as the new U.S. senator from Massachusetts to fill the seat formerly held by the late Sen. Ted Kennedy, and immediately signaled opposition to President Obama's spending plans.
Brown's new Senate colleagues applauded after the ceremony on the floor of the Senate chamber conducted by Vice President Joe Biden, in his capacity as president of the Senate. Democratic Sen. John Kerry, also of Massachusetts, and Brown's wife, Gail Huff, accompanied Brown into the chamber.
At a news conference after the ceremony, Brown thanked Massachusetts voters who gave him a surprise victory in the January 19 special election in a state that had not elected a Republican senator since 1972.
"I can't promise I'll be right in every vote I make. I'm sure I'll make mistakes from time to time," Brown said. "But I will try to learn and grow and do the very best job I can on a day-to-day basis."
Brown's election victory stripped Senate Democrats of their 60-seat Senate supermajority, imperiling the ability of Obama and Democrats to push major legislative priorities such as health care reform through Congress.
The Republican upset in Massachusetts also raised fears among many congressional Democrats of a potential GOP landslide in November's midterm elections.
A fiscal conservative who holds some moderate views, Brown was noncommittal on whether he would support a Republican filibuster in coming Senate consideration of some Obama nominees for government posts.
He also said he needed to talk to generals in the field before deciding to support Obama's call, supported by top military leaders, to repeal the "don't ask, don't tell" policy regarding a ban on gays in the military.
Brown made clear he opposes the spending policies of the Obama administration, stating that the $862 billion stimulus bill passed last year "didn't create one new job" in Massachusetts or across the country. He also said Congress should start over on health care with bipartisan talks, instead of continuing work on separate comprehensive bills passed by the House and Senate.
That prompted a response later from Jay Carney, spokesman for Biden, who said, "Anyone can go to recovery.gov (on the Internet) and see that Massachusetts state and local government, businesses and community organizations have already reported directly funding over 9,000 jobs in the state last year -- and that's based on a only a portion of the total $8.4 billion in (stimulus) funds that have already gone to Massachusetts."
He also said Congress should start over on health care with bipartisan talks, instead of continuing work on separate comprehensive bills passed by the House and Senate.
At the same time, Brown said he would consider each piece of legislation on merit, rather than whether it was proposed by one party or another.
"If I see a bill that's good for my state first, I don't care where it comes from," Brown said. "If it's good for Massachusetts, I'll consider it."
Thursday's ceremony occurred a week earlier than originally planned.
Massachusetts officials had said it would take a few weeks after the election to certify the result of Brown's victory. In a letter to Massachusetts Gov. Deval Patrick and Secretary of State William Galvin on Wednesday, Brown's attorney said the senator-elect had planned on being sworn in on February 11, but had been told that several Senate votes would be held before then.
"For this reason, he wants certification to occur immediately," attorney Daniel Winslow wrote.
The certification occurred Thursday, allowing Brown to officially fill his seat later in the day.
"There's no hidden agenda," Brown said of his push to get certified this week instead of next. "It's because I want to get to work."
Asked why his daughters didn't attend the swearing-in, Brown explained one of them, Ayla, had a college basketball game to play Thursday and the other, Arianna, had a college exam.
"The Bibles I used for today's swearing-in belong to my daughters, and I stacked them one on top of the other and took my oath on them," Brown said.
Brown will be taking over Kennedy's coveted office space in the Senate Russell building. Sen. Paul Kirk, who was appointed to fill the seat after Kennedy's death, currently occupies the office and will move out.
Several Senate sources tell CNN that the Senate Rules Committee, which assigns office space, decided to give Brown the office space as a matter of convenience.
Because of his seniority, Kennedy had one of the most coveted office suites in the Senate complex. It is located in the Russell building, down the hall from the Rotunda, and has balconies that overlook the Capitol.
CNN Senior Congressional Correspondent Dana Bash contributed to this report.