Barrack Obama

"People start thinking behavior that in normal times we would consider completely unacceptable and outrageous becomes normalized," Obama said during a news conference at the tail end of his visit to Laos.

"People start thinking that we should be grading on a curve," he said. "But I can tell you from the interactions I have had over the last eight or nine days with foreign leaders that this is serious business."

The forum offered a preview of how the two candidates will present themselves to the country when they appear on stage September 26 at the crucial first presidential debate. The gulf between them was especially apparent when the discussion centered on Russia and combating ISIS.

Clinton has repeatedly slammed Trump on the campaign trail for his embrace of Russian President Vladimir Putin. But at the "Commander in Chief" forum hosted by NBC News, Trump once again praised the Russian leader in comparison to President Barack Obama.

A White House official said that Obama had a "brief discussion" with Philippine President Rodrigo Duterte ahead of a gala dinner in the Lao capital marking the beginning of the yearly ASEAN summit.

The meeting took place in a holding space for leaders, the official said, adding the "exchange consisted of pleasantries between the two."

Duterte was likely keen to clear the air after publicly scoffing earlier this week at suggestions that Obama would raise the issue of extrajudicial killings during their planned meeting.

A foul-mouthed outburst cost the new leader of Washington's key Pacific ally a chance to meet President Barack Obama in Laos on Tuesday. Duterte blasted Obama as a "son of a bitch" and warned he would not tolerate any violation of Philippines sovereignty he said such a question would entail, after which the White House canceled their planned parley.

His controversial comments have led to diplomatic consequences with the US president cancelling a scheduled meeting with Mr Duterte.

But the Philippine leader, who has insulted prominent figures before, is not the only one guilty of offending world leaders.

From a "sadistic nurse" to "the devil" himself, here are some of the more memorable comments made by or about those in positions of power.

Arafat the 'son of 60,000 whores' (1999)

Duterte, who cursed Obama as a "son of a bitch" Monday, said in a statement through his spokesman that he regretted "it came across as a personal attack on the US President."

"We look forward to ironing out differences arising out of national priorities and perceptions," the statement released on Tuesday read.

"The heat has to be turned up so much that as a community, we've got to hold our vote," Diddy told the Rev. Al Sharpton on MSNBC Sunday. "Don't pacify yourself; really revolutionize the game. Make them come for our vote. It's a whole different strategy, but I think we need to hold our vote because I don't believe any of them."

The entertainment icon explained that while he thinks that Obama has done "an excellent job" as president, he also feels that the first black presidency didn't fully deliver on its promise.

"I wouldn't overcrank the significance" of tensions at the airport, Mr Obama told a news conference in the Chinese city of Hangzhou, where global leaders are convening for a summit.

Mr Obama's last scheduled trip to China before leaving office got off to an awkward start soon after Air Force One landed in Hangzhou when a Chinese security official blocked National Security Adviser Susan Rice on the tarmac.

He prevented her from walking to the motorcade as she crossed a media rope line, speaking angrily to her before a Secret Service agent stepped between the two.

He made the comments during a "candid exchange" with his Chinese counterpart, Xi Jinping, in Hangzhou before the G20 summit, the White House said.

In July, an international tribunal ruled against Chinese claims to rights in the South China Sea.

China dismissed the ruling and said it would not be bound by it.

National Geographic reported Friday that the maroon and gold creature, which was discovered 300 feet deep in the waters off Kure Atoll, is the only known fish to live within Papahānaumokuākea, an expanse of coral reefs and seamounts home to more than 7,000 species.

One looking for the fish's official name, however, is likely to stay hooked -- a formal description of the species isn't expected to be published until later this year.