WASHINGTON » Tempering his historic Cuba policy shift with a dose of realism, President Barack Obama said Friday that change might not come quickly to the communist island. He suggested Congress will keep the U.S. economic embargo in place until lawmakers can gauge the pace of progress in the "hermetically sealed society."

Still, Obama’s surprise announcement this week that the U.S. was ending its Cold War diplomatic freeze with Cuba appeared to have contributed to energizing the president as he closes a difficult sixth year in office.

"My presidency is entering the fourth quarter," Obama said at a year-end White House news conference shortly before leaving for a two-week Hawaii vacation. "Interesting stuff happens in the fourth quarter."

On domestic matters, Obama was measured about the prospect of forging compromises with the new Republican majority on Capitol Hill, and he warned the GOP that he would block efforts to dismantle his health care law or further water down banking regulations. He made no commitment to sign the first bill incoming Senate Majority Leader Mitch McConnell has vowed to take up: approval of the Keystone XL oil pipeline. Obama said the project’s value has been exaggerated.

The president spoke shortly after the FBI formally accused North Korea of hacking Sony Pictures Entertainment. Obama promised to respond to the cyberattack "in a place and manner and time that we choose." But he also criticized Sony for shelving the satirical film about a plot to assassinate North Korea’s leader that sparked the attack, saying the entertainment company "made a mistake."

Despite Obama’s upbeat mood as 2014 comes to a close, his sixth year in office has been one of fits and starts. His agenda was frequently overshadowed by a broad array of crises, including the rise of Middle Eastern militants, Russia’s actions in Ukraine, a surge of unaccompanied minors to the U.S.-Mexican border from the south and an Ebola outbreak in West Africa that brought fears to this country. Obama’s Demo­cratic Party suffered sweeping losses in a midterm election where the president was deemed too unpopular to participate.

Yet Obama pointed to the decline in the nation’s unemployment rate, increased economic growth and numerous states and cities enacting minimum wage increases that the president has championed.

Obama also seemed to find his footing after the election, unveiling executive actions on immigration and striking a surprise climate change deal with China, both of which were greeted by accusations of presidential overreach from Republicans. On Wednesday he unilaterally ended the Cold War-era diplomatic freeze with Cuba, the communist island just 90 miles off the U.S. coast.

The policy shift with Cuba is among the most substantial foreign policy actions of Obama’s presidency. But he said he doesn’t expect decades of dictatorship on the island to end quickly and said he shared Cuban dissidents’ concerns about the country’s poor human rights record.

"This is still a regime that represses its people," Obama said. He expressed an interest in visiting Cuba at some point in his life but suggested that visit might have to wait until after his presidency.

During his 17-day break in Hawaii, Obama is expected to spend some time crafting his State of the Union address, in which he will outline his goals for working with the GOP-led Congress. House Speaker John Boehner has invited Obama to address a joint session of Congress on Jan. 20.

The president has already raised the prospect of reaching accords with Republicans on trade, which is a rare area of agreement between the White House and the GOP. And Obama said his staff would be talking to Republicans in the coming weeks to start work on overhauling the nation’s complicated tax code, though both sides acknowledge that their differences on the complex issue run deep.

"I’m being sincere when I say I want to work with this new Congress to get things done," Obama said.