 -- Former President Barack Obama today offered an optimistic vision for the future, but condemned the latest attempt by Republicans to repeal his signature legislation, the 2010 Affordable Care Act, calling the efforts "aggravating.”

“When I see people trying to undo that hard-won progress for the 50th or 60th time with bills that would raise costs or reduce coverage, or roll back protections for older Americans or people with pre-existing conditions -- the cancer survivor, the expecting mom or the child with autism, or asthma, for whom coverage once again would be almost unattainable -- it is aggravating,” Obama said at the Gates Foundation’s "Goalkeepers" event in New York.

“And all of this being done without any demonstrable economic or actuarial or plain common sense rationale, it frustrates," he added. "And it is certainly frustrating to have to mobilize every couple of months to keep our leaders from inflicting real human suffering on our constituents.”

Obama joked about recent disagreements in the United States about universal health care coverage, a tenet of Sen. Bernie Sanders' presidential campaign platform in 2016 that has since gained steam in the Democratic Party.

“Those of you who live in countries that already have universal health care are trying to figure out what's the controversy here,” Obama said to laughter. “I am, too.”

In keeping with the unwritten tradition that former presidents don’t outright disparage a sitting president, Obama did not criticize President Donald Trump by name. But he expressed his frustration with the current administration on another achievement during his presidency, addressing climate change through the Paris climate agreement. But he said progress can still be made by people outside the White House.

“Even if at the current moment the federal government is not as engaged in these efforts as I would like, nevertheless, progress continues because of the efforts of people like Bill [Gates] and a whole host of entrepreneurs and universities and cities and states,” Obama said.

“They are making change around energy policy in America separate and apart from what government is doing. And that gives me confidence that we can continue to make progress.”

Despite his overall optimism, Obama also warned about the rise of nationalist impulses in politics.

“The rise of nationalism and xenophobia in politics that says it's not ‘we’ but ‘us and them’ — a politics that threatens to turn good people away from the kind of collective action that has always driven human progress. … These are real challenges. And we can't sugar coat them.”