US President Barack Obama has said he may speak out after leaving office if he feels his successor Donald Trump is threatening core American values.
By convention, former presidents tend to leave the political fray and avoid commenting on their successors.
Mr Obama said he would give Mr Trump time to outline his vision but added that, as a private citizen, he might speak out on certain issues.
Mr Trump spent the weekend interviewing candidates for top jobs in his cabinet.
"I want to be respectful of the office and give the president-elect an opportunity to put forward his platform and his arguments without somebody popping off," Mr Obama said at a forum in Lima, Peru.
But, he added, if an issue "goes to core questions about our values and our ideals, and if I think that it's necessary or helpful for me to defend those ideals, then I'll examine it when it comes".
The president described himself as an "American citizen who cares deeply about our country".
Speaking at a news conference to mark the end of the Asia-Pacific Economic Cooperation (Apec) summit, Mr Obama reiterated that he would extend to Mr Trump's incoming administration the same professional courtesy shown to his team by his predecessor George W Bush.
Mr Bush has refrained since leaving office from commenting on Mr Obama's presidency. "I don't think it does any good," he told CNN in 2013, after Mr Obama was elected for a second time.
"It's a hard job. He's got plenty on his agenda. It's difficult. A former president doesn't need to make it any harder. Other presidents have taken different decisions; that's mine."
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Mr Bush's stance falls in line with tradition. US presidents tend to avoid criticising predecessors or successors. Mr Obama was clear that he would not weigh in on Mr Trump's decisions while he was still in office.
But his suggestion that, as a private citizen, he would seek to defend "core values" comes amid mounting concern among civil rights groups and others about Mr Trump's political appointments.
The president-elect's chief strategist, Steve Bannon, was previously the head of Breitbart, a website accused of promoting racism and anti-Semitism. And Mr Trump's national security adviser, Gen Michael Flynn, has previously likened Islam to a "cancer" spreading through the US.
Mr Trump's nominee for attorney general, Jeff Sessions, lost the chance to become a federal judge in 1986 because of allegedly racist remarks.
Mr Obama said he believed the intense responsibility of the presidency would force Mr Trump to moderate some of the more extreme policy positions he had advocated during his campaign.
On Sunday the incoming president indicated he had made more selections after a weekend of interviews at his golf resort in New Jersey, saying: "We really had some great meetings, and you'll be hearing about them soon."
Mr Trump has confirmed he is considering retired Marine Corps Gen James Mattis for the role of defence secretary, calling him "very impressive" in a tweet. He also met former critic Mitt Romney, who is now being considered for secretary of state.
Mr Trump also says that his wife, Melania, and their 10-year-old son Barron will not move into the White House straight away. They would move "very soon, right after he finishes school", he said. The US school year runs from late August or early September until late May or June.
Mr Obama, meanwhile, said his first priority after leaving office was to take his wife, Michelle, on holiday, and "get some rest, spend time with my girls and do some writing, do some thinking".
Asked about the failure of the Democratic party's campaign under Hillary Clinton, Mr Obama criticised the "micro-targeting" of "particular, discrete groups", arguing there should have been an effort to reach out to the entire country.
Mrs Clinton has been criticised for focusing her energy on certain demographics, including Latinos and women, who were believed to support her, at the expense of a more inclusive campaign.
That approach "is not going to win you the broad mandate that you need", Mr Obama said, adding that the party needed a "smarter message".