Nothing stops politics this election season -- not even the water's edge. 

While traveling overseas on official business Thursday, President Obama couldn’t resist wading into political matters back home, sparking controversy by saying foreign leaders are “rattled” by the rise of presumptive Republican nominee Donald Trump. 

Obama, saying leaders have "good reason" to feel that way, made the remarks on the sidelines of a Group of Seven economic summit in Japan.

"They are rattled by it — and for good reason," Obama said. "Because a lot of the proposals he has made display either ignorance of world affairs, or a cavalier attitude, or an interest in getting tweets and headlines."

He contrasted that with proposals he said thoughtfully address what's required to keep the U.S. safe and "to keep the world on an even keel."

Trump, though, brushed off Obama's put-down later in the day. Speaking ahead of an address in North Dakota, Trump said: "That's a good thing, I love that word."

"In business, when you rattle someone, that's good," Trump said. "If they're rattled, in a friendly way, that's a good thing ... not a bad thing." 

Trump also touched on remarks Obama made at a campaign stop in Billings, Montana, saying, "he said other countries are nervous. I say it’s good if they’re nervous." 

Obama, meanwhile, was criticized for his remarks by other Republicans, with one calling them “incredibly irresponsible” given the context. 

“When the president of the United States goes overseas he’s representing the country,” Josh Holmes, former chief of staff to Senate Majority Leader Mitch McConnell, said on Fox News. “It is remarkably irresponsible and remarkably unpresidential for him to weigh in on a domestic political battle and effectively undermine one of the candidates who could replace him next January.”

“In front of the world community and effectively in front of all the world leaders, saying someone is essentially unfit for office is an incredibly irresponsible move for the president of the United States,” Holmes said.

Questions about Trump have followed Obama on his travels abroad, with world leaders expressing concern about certain aspect of Trump’s campaign, most notably his plan to temporarily ban Muslim immigration and his positions on trade.

Trump has also threatened to renegotiate Obama’s nuclear deal with Iran and the global climate treaty reached in Paris. As Obama was warning world leaders Thursday about Trump, a newly released Associated Press tally showed he has now attained the number of delegates needed to clinch the GOP nomination. 

Obama made the remarks a day before he visits Hiroshima, and said other countries pay more attention to the U.S. elections as they depend on America to provide stability and direction.

"I think it's fair to say they are surprised by the Republican nominee," Obama said, referring to Trump.

The Associated Press contributed to this report.