Joe Biden is thanking Democratic supporters in the afterglow of U.S. President Barack Obama's second inauguration, dropping hints that he may try to cement Obama's legacy with his own presidential campaign in 2016.

The U.S. Vice-President packed his schedule with events and receptions attended by party insiders surrounding Obama's inauguration, giving him a chance to thank prominent lawmakers and donors and plant the seeds for a future bid. It comes on the heels of the vice-president's prominent role in brokering a compromise on the "fiscal cliff" standoff with Congress and developing gun-control legislation after December's deadly elementary school shooting in Connecticut.

Secretary of State Hillary Rodham Clinton remains the heavy favourite of the Democratic party faithful, but Biden is making clear that he has no intention of closing any doors that could lead to the White House, especially if Clinton decides not to run.

As vice-president, Biden can stay in the spotlight, and he is no stranger to the rigours of a presidential campaign after two unsuccessful bids, in 1988 and 2008. The former Delaware senator has racked up a long list of domestic and foreign policy achievements, even as his occasional off-script moments have become fodder for Republican critics.

"There's a whole lot of reasons why I wouldn't run," Biden, who will be nearly 74 on Election Day in 2016, told CNN before the inauguration. "I don't have to make that decision for a while. In the meantime, there's one thing I know I have to do, no matter what I do. I have to help this president move this country to the next stage."

Yet with his high-profile perch, Biden is doing nothing to tamp down the speculation.

Biden 'deeply admired'

Biden's private swearing-in ceremony Sunday was attended by recently elected New Hampshire Gov. Maggie Hassan, someone who would be a potent ally in the state's first-in-the-nation primary. Attendees at a Sunday afternoon reception at the vice-president's residence at the Naval Observatory said they noticed a lot of party activists from early voting states like New Hampshire, Iowa and South Carolina.

During the weekend, Biden attended several balls with Democrats who would energize a presidential campaign. At the Iowa State Society Inaugural Ball, Biden told partygoers he was "proud to be president of the United States," prompting cheers. He quickly corrected himself, saying he was "proud to be vice-president of the United States, but I am prouder to be ... President Barack Obama's vice-president." Laughing it off, he said, "There's goes that."

At a ball celebrating Latino voters, Biden said the Hispanic community was "a decisive factor" in the election. "This is your moment," Biden said. "America owes you." Some party stalwarts said it was noteworthy that Biden asked Supreme Court Justice Sonia Sotomayor, the first Latina justice, to administer the oath of office.

At a ball honouring environmentalists, sponsored by the National Wildlife Federation and other environmental groups, Biden said the Obama administration was committed to confronting climate change. "I don't intend to let these four years go by without getting a hell of a lot done" on the environment, Biden said.

On Inauguration Day, Biden and his wife, Jill, walked part of the parade route, waving to the cheering crowds in a made-for-TV moment. At one point, the vice-president even jogged across Pennsylvania Avenue to shake hands with "Today" show weatherman Al Roker, a clip that the morning show played repeatedly the following day.

"It seems obvious that he's going to keep that option open for himself and do the right things," said Mike Gronstal, the Democratic leader of the Iowa state Senate, who attended the Naval Observatory reception. Gronstal said Biden actively worked the room, thanking supporters for their help during the 2012 campaign.

On Tuesday afternoon, Biden met with members of the Democratic National Committee at a private reception after a DNC meeting, where delegates unanimously re-elected Florida Rep. Debbie Wasserman Schultz to another term as chair.

A long line of DNC members spilled into the lobby before the reception and REO Speedwagon's "Roll With the Changes," a frequently played campaign theme song, could be heard from outside the room. Attendees said Biden thanked them for their work and offered an upbeat assessment of the second term, mingling with party leaders and posing for photographs during the gathering.

If Clinton decides not to run, Biden could draw upon good will from Obama's voting coalition, an ability to connect with regular folks and extensive campaigning in key states like Iowa, New Hampshire, Florida and Ohio. But he would also need to deal with personal poll numbers that rank below Obama's and a propensity to commit foot-in-mouth moments in an era where political gaffes can quickly sink a campaign.

New Hampshire state Sen. Martha Fuller Clark, who was among the attendees at Biden's Sunday reception, said it was "early to read into" Biden's interest in 2016 but said there was "huge support" in the key primary state.

"He's deeply admired and loved in New Hampshire," Clark said. "Clearly, Joe Biden occupies a key place in our hearts."