And he acknowledged a major foreign policy failure, saying that his approach to the conflict in Syria had fallen short. Obama balked at sending US ground troops to fight there and emphasized need for a political solution to the carnage. He also held back from giving major support or significant weaponry to moderate Syrian rebels fighting the regime of Syrian President Bashar al-Assad.
"I recognize that that has not worked," Obama said at a White House news conference.
"It is something that I continue to think about every day and we continue to try to find some formula that would allow us to see that suffering end," Obama said.
He was responding to a question about President-elect Donald Trump's recent suggestion that he would pull US support from the Syrian opposition, as well as campaign vows to gut, rework or void international agreements on climate change and Iran's nuclear program.
"It becomes more difficult to undo something that's working than undo something that isn't working," Obama said, citing the success of the Iran pact and the accomplishment of getting almost 200 nations to ratify the Paris Agreement on climate change climate.
The President also cited tradition. "These international agreements, the tradition has been, you carry them forward across administrations," Obama said, "particularly if you find they're good for us."
Obama was asked about Trump's vow to undo the Iran nuclear agreement finalized in July 2015 after negotiations between Iran, the US, Germany, the UK, France, Russia and China.
Trump repeatedly bashed the Iran deal during the campaign, disparaging it as "terrible" and declaring in March at the American Israel Public Affairs Committee that his "No. 1 priority is to dismantle the disastrous deal with Iran."
Obama said that Trump would find it hard to do so, particularly because Iran has complied with the deal over its first year.
Trump will also have to consider the impact on America's closest allies, Obama added.
"For us to pull out would require us to start sanctioning those other countries that were still abiding by the deal because from their perspective they were still abiding" by the deal, Obama said.
Mark Dubowitz, executive director of the Foundation for the Defense of Democracies and a critic of the agreement, said Trump is "likely to enforce the Iran deal but to treat any violation of the deal -- no matter how small -- as grounds to re-impose sanctions" allowed under the pact.