The 82-year-old United States president's silence on a looming government shutdown over Christmas is just the latest example of how critics say the aging leader is in office but not in power.

Despite still occupying the world's most powerful pulpit, Biden has remained virtually absent from the public debate about his noisy successor whom he often used to brand as a threat to democracy.

While Biden stays largely off the radar, it is Trump who increasingly calls the shots, whether by carrying out his own shadow foreign policy or by torpedoing a deal to fund the government.

"This is a Biden problem to solve!" Trump said on his TruthSocial network on Friday.

A White House spokesperson declined to comment on whether Biden would take any action on the shutdown when asked by AFP, pointing instead to a written statement by his Press Secretary Karine Jean-Pierre on Thursday.

Jean-Pierre said Biden supported an original bipartisan funding agreement "not this giveaway for billionaires."

'Sprint to the finish'

It was always going to be a painful exit for Biden, after he was forced to drop out of the 2024 election in June following a disastrous debate against Trump.

He handed over the Democratic nomination to Vice President Kamala Harris yet was widely reported to have believed that he could have succeeded where she failed against the Republican. 

The White House insists that Biden is in what his chief of staff Jeff Zients called a "sprint to the finish line" to preserve his legacy before the January 20 handover of power.

In recent weeks he has unveiled a string of last-gasp efforts to "Trump-proof" policies on everything from student loan forgiveness to the economy. He gave televised speeches to hail a ceasefire in Lebanon and to claim credit for the fall of Syrian President Bashar al-Assad. while his administration is still pushing for a truce in Gaza.

United States President Joe Biden (right) is induced to the Department of Labor Hall of Honor by Acting Secretary of Labor Julie Su during a ceremony at the Department of Labor on Dec. 16, 2024 in Washington, DC. Biden signed a proclamation to establish the Frances Perkins National Monument in Maine, dedicated to Perkins who was the first female Cabinet secretary and served as the Labor Secretary under Franklin D. Roosevelt. (AFP/Getty Images/Kevin Dietsch)

In an article for the American Prospect website, Biden said he wanted to "take stock" of his economic achievements.

"It will take years to see the full effects in terms of new jobs and new investments all around the country, but we have planted the seeds that are making this happen," he said.

Yet sometimes his efforts have often underscored how America's oldest president is fading away more than going out with a bang.

Biden coughed throughout what was meant to be a showpiece speech to trumpet his economic legacy last week, and which came shortly after a lively Trump press conference.

He has meanwhile embarked on foreign trips that were meant to highlight his status as a global statesman and reassure allies unsure what Trump's return meant for them. The effect was sometimes the opposite. 

'Diminished'

Biden appeared frail in a trip to the Amazon during which he momentarily looked like he was wandering off into the jungle, and missed a group photo with G20 leaders in Brazil when they refused to wait for him.

In Angola, making a long-promised first trip of his president to sub-Saharan Africa, Biden appeared to be resting his eyes for several periods during a summit, while Angola's president took him by the arm to guide him up a short flight of steps.

Moreover, the man who was once one of the most garrulous politicians in Washington has been almost silent in the face of reporters' questions.

Biden has in particular declined to say whether he still believes Trump remains a threat to democracy, despite repeatedly condemning the Republican during the campaign for his actions during the Jen. 6, 2021 attack on the US Capitol.

He has also refused to comment on perhaps his most prominent act since the election defeat, a pardon for his troubled son Hunter on gun and tax charges.

The sense of a Biden fade-out has not been helped by a proliferation of stories in US media about his decline.

The Wall Street Journal reported this week that White House gatekeepers built a wall around a "diminished" Biden during his presidency, keeping meetings short and controlling access.

The White House denied that Biden had declined physically or mentally, it said.