Donald Trump may not be able to pursue many of the pledges he made during his election campaign, US President Barack Obama has said.
Mr Obama said he can guarantee that reality will force the president-elect to adjust how he approaches many issues.
Speaking at the Asia-Pacific Economic Cooperation (APEC) summit, the outgoing president suggested he would speak out if Mr Trump or his policies breach certain "values or ideals".
Mr Obama suggested that once he is out of office he would uphold the tradition of ex-presidents stepping aside quietly to allow their successors space to govern.
But he added: "As an American citizen who cares deeply about our country, if there are issues that have less to do with the specifics of some legislative proposal or battle or go to core questions about our values and ideals, and if I think that it's necessary or helpful for me to defend those ideals, I'll examine it when it comes."
The president spoke out throughout the election campaign against Mr Trump's calls for banning Muslim immigrants, deporting millions of people living in the US illegally, reinstituting waterboarding, repealing "Obamacare" and cancelling the Paris climate deal.
Mr Obama said people should take a "wait and see" approach to how the Republican's policy proposals match up with his campaign rhetoric.
On his final day in Peru, Obama spoke briefly with Russian president Vladimir Putin about Ukraine and the Syria crisis.
The four-minute conversation, likely the leaders' last face-to-face interaction, came amid intense speculation and concern about whether Mr Trump's election might herald a more conciliatory US approach to Russia.
Mr Obama said he told the Russian President the US remains deeply concerned about the bloodshed and situation in Syria and reiterated the need for a ceasefire, but said he was "not optimistic" about the country's short-term prospects.
Mr Putin, speaking later in Lima, said he and Mr Obama had noted that while their working relationship had been difficult, they'd "always respected each other's positions - and each other".