Former President Obama touched on growing divisions within his own party, warning against pushes for ideological purity that can result in a “circular firing squad” in a town hall organized by The Obama Foundation in Berlin today.

While taking audience questions about the frustration that comes with lack of change, Obama expressed concern about a lack of compromise in Washington, and said he specifically worries progressive politicians could be alienating potential allies.

“One of the things I do worry about sometimes among progressives in the United States — maybe it’s true here as well — is a certain kind of rigidity where we say, ‘Oh, I’m sorry, this is how it’s going to be,’” Obama said. “And then we start sometimes creating what’s called a ‘circular firing squad’ where you start shooting at your allies because one of them is straying from purity on the issues.”

Obama said he believes this approach “weakens” movements, and that those that would like to see a progressive agenda “have to recognize that the way we’ve structured democracy requires you to take into account people who don’t agree with you.”

Obama was indirectly sending a message to Rep. Alexandria Ocasio-Cortez (D-NY) who has vowed to support primary opponents against fellow Democrats.

Earlier this year Ocasio-Cortez appeared in a video released by Justice Democrats, a far-left group focused on going to war with incumbent Democrats who are not progressive enough.

Justice Democrats leaders admit the group’s tactics are similar to the tea party on the right, emphasizing less coalition building and more ideological purity.

Some Democrats have privately whispered that Ocasio-Cortez’s tweet-first, ask-questions-later mentality reminds them of President Trump.

“That combat approach is going to upset a lot of people,” said ACLU political director Faiz Shakir, a former senior adviser to Democratic Leaders Harry Reid and Nancy Pelosi. “What she’s suggesting is the way I’m going to get people is by carrying a stick.”

The effort to purge a political party by mandating purity usually results in a more exclusive, and less inclusive party.

Obama emphasized that during his days as a community organizer he also “wanted change now and I wanted 100% of what I wanted,” but he later realized that getting things done often takes compromise.

“So I think whether you are speaking as a citizen or as a political leader or as an organizer,” he continued, “you have to recognize that the way we structure democracy requires you to take into account people who don’t agree with you, and that by definition means you’re not going to get 100 percent of what you want.”

Obama ended his speech by advocating for patience and incremental change: “We have to be careful in balancing big dreams and bold ideas with also recognizing that typically change happens in steps. And if you want to skip steps, you can. Historically what’s ended up happening is sometimes if you skip too many steps you end up having bad outcomes.”

WATCH: Obama Town Hall

Obama also encouraged people to take a more active role in government, arguing citizens with new ideas should reach out to politicians who are open to them.

“Sometimes we think of the government as this ‘thing’ that is separate from us,” Obama said. “But if we’re active citizens, then part of our job is not just to get government to respond to you — it’s also to improve the government.”

He added, “The point I’m making is, in addition to electing good people, one of the things that you can do, I think, is encourage and work with governments to identify where are bottlenecks, where are inefficiencies that could potentially be solved and then finding allies to help improve processes inside of government.”

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In an Obama Foundation event earlier this year, Obama called for “new blood” in the political ranks, but new, progressive House Democrats have at times found themselves at odds with more established party figures over issues from refusing to take corporate PAC money to big ideas like Medicare-for-all and the Green New Deal.

For the most part, however, Democrats have been following Obama’s lead and been careful to maintain unity in public.