US President holds farewell press conference

Obama has given over 150 news conferences since becoming head of state eight years ago. His last takes place two days before he turns over the Oval Office.

The outgoing Democratic leader had vowed a smooth transition of power to the Republican Trump, but the reality has been a little more tricky.

The 44th and 45th presidents have traded barbs in public and the incoming administration has faced a momentous challenge to staff-in in time for Friday's first day at work.

Trump spokesman Sean Spicer sought to play down any troubles, praising Obama and his staff and saying this transition may come to be seen as a "gold standard."

Still, Obama's words will be carefully scrutinized, no more so than by the 70-year-old president-elect, who has proven quick to retaliate at any slight.

His words will also carry extra political weight thanks to his popularity: his approval rating stands at 60 percent -- according to a CNN/ORC poll -- the highest level since June 2009.

On Tuesday, Trump dismissed the polls as "rigged" after a Washington Post-ABC News survey found his 40 percent approval rating was the lowest of any incoming president-elect since Jimmy Carter in 1977.

Even the venue for Obama's press conference -- the White House briefing room, has taken on political significance.

Trump's team has floated the idea of evicting the White House press corps from the West Wing, ending daily on-camera briefings and handpicking who gets access, although some of those suggestions have since been rowed back.

Obama's outgoing press secretary, Josh Earnest, used his final briefing Tuesday to defend opening the White House doors to the press, saying harsh questioning had held the administration to account and made Obama a better president.

"It's uncomfortable to be in a position of authority, certainly a position of responsibility, and to be subjected to those kinds of questions," Earnest said.

"That's true even when you're doing the right thing for the right reasons. But it's a necessary part of our democracy."

When president George W. Bush was on his way out the door he voiced a similar sentiment.

"Sometimes didn't like the stories that you wrote or reported on. Sometimes you 'misunderestimated' me," he joked. "But always the relationship I have felt has been professional. And I appreciate it."

Obama may not be quite so effusive. While defending the press, he has been a searing critic of shallow and flitting reporting.

Obama is likely to weigh in on his controversial decision to slash the sentence of transgender army private Chelsea Manning, who was jailed for 35 years for handing classified US documents to WikiLeaks.

On Wednesday, Obama pardoned 64 people and commuted the sentences of 209 others -- including 29-year-old Manning, who will now be released in May -- in one of his final acts as president.

Manning was convicted in August 2013 of espionage and other offenses, after admitting to the leak of 700,000 sensitive military and diplomatic documents.

The cache included military logs from wars in Iraq and Afghanistan and cables offering sensitive -- and often embarrassingly bareknuckle -- diplomatic assessments of foreign leaders and world events.

Trump's spokesman Spicer joined fellow Republicans in condemning that move Wednesday, describing it as "disappointing."

"It sends a very troubling message," he said, adding that the decision was a "bit of irony and double standard" given Democrats' outcry over Russian election-related hacking.