At a joint news conference with German Chancellor Angela Merkel, March 17, President Trump seemed to suggest he stands by his claim that the Obama administration conducted surveillance on his 2016 presidential campaign. He also said he "seldom" regrets any of his tweets. (Reuters)

President Trump made a kind-of-joke toward the end of his news conference with German Chancellor Angela Merkel on Friday.

“As far as wiretapping, I guess by this past administration, at least we have something in common, perhaps,” Trump said. He was referring to the actual wiretapping of Merkel for which President Barack Obama apologized in 2013 and the still evidence-free allegation Trump has made that Obama tapped his phones.

Merkel reacted about like you might expect.

So here we have a president of the United States bringing his conspiracy theories into a news conference with a top foreign leader and ally — re-upping a claim for which bipartisan congressional leaders have said there is still no evidence.

And that wasn't even the only conspiracy theory Trump delved into during their brief appearance together. During the same news conference — and related to the same subject — Trump made no apologies for White House press secretary Sean Spicer having passed along an allegation Thursday that Obama used British intelligence to spy on Trump. Trump noted that Spicer was merely citing Fox News analyst Judge Andrew Napolitano, who alleged that the U.K.'s Government Communications Headquarters (GCHQ) did the spying for Obama.

“That was a statement made by a very talented lawyer on Fox, and so you shouldn't be talking to me, you should be talking to Fox,” Trump said. “Okay?”

Trump isn't exactly projecting skepticism about Napolitano's claim, to say the least.

That's two of the United States' top allies — Great Britain and Germany — getting wrapped up in Trump's wiretapping conspiracy theories in the span of 24 hours.

As the Monkey Cage's Henry Farrell notes, Britain was already rather upset about Spicer's claim, and that's only likely to increase after Trump's comments Friday afternoon. (There had been some reporting that the Trump White House apologized, but the White House now denies this.)

And Merkel seemed to make clear her own feelings about her situation being compared to Trump's during the news conference.

Concerns about Trump's temperament and reliability have always been more acute when it came to his handling of foreign affairs. It's one thing to be volatile when talking about domestic issues; it's another to say the wrong thing to a foreign power and to be unable to grasp the delicate dance of diplomacy.

These comments suggest that Trump really isn't concerned about all of that. He's perfectly willing to make his bold and evidence-free claims even when it might make things awkward with a top ally.