Former President Barack Obama and President-elect Donald Trump had what appeared to be a warm conversation Thursday ahead of former President Jimmy Carter’s funeral, but a professional lip reader told The Post their smiles and laughter belied more serious substance.

Trump, 78, possibly wary of cameras facing the pair as they sat shoulder to shoulder in the pews, cautioned Obama, 63, that they would have to “find a quiet place” later in the day to discuss a “matter of importance,” according to forensic lip reader Jeremy Freeman.

It’s unclear what precisely that conversation would entail, but Obama and Trump appeared to be discussing international agreements, according to Freeman’s translation.

At one point, Trump leaned toward Obama and said, “I’ve pulled out of that. It’s the conditions. Can you imagine that?”