News photos of President Barack Obama bowing to Japan's emperor have incensed critics here, who said the US leader should stand tall when representing America overseas.

Obama on Monday was in China, having wrapped up the Japan leg of his Asia trip two days earlier. But Washington's punditocracy was still weighing whether or not the US president had disgraced his country two days earlier by having taken a deep bow at the waist while meeting Japan's Emperor Akihito.

Obama isn't the first American president to do so. Back in the 1980s, Republican president Ronald Reagan was criticized after bowing to Queen Elizabeth the first time he met her, and President George W. Bush bowed before Saudi Arabia's king while being presented with a medal.

Political talk shows have played and replayed the moment from the second day of Obama's week-long Asia tour, which set the blogosphere on fire and chat show tongues wagging.

"I don't know why President Obama thought that was appropriate. Maybe he thought it would play well in Japan. But it's not appropriate for an American president to bow to a foreign one," said conservative pundit William Kristol speaking on the Fox News Sunday program, adding that the gesture bespoke a United States that has become weak and overly-deferential under Obama.

Another conservative voice, Bill Bennett, said on CNN's "State of the Union" program: "It's ugly. I don't want to see it."

"We don't defer to emperors. We don't defer to kings or emperors. The president of the United States -- this coupled with so many apologies from the United States -- is just another thing," said Bennett.

Some conservative critics juxtaposed the image of Obama with one of former US vice president Dick Cheney, who greeted the emperor in 2007 with a firm handshake but no bow.

"I'll bet if you look at pictures of world leaders over 20 years meeting the emperor in Japan, they don't bow," Kristol said.

Some said the gesture was particularly grating coming after Obama's bow to Saudi Arabia's King Abdullah at a G20 meeting in April.

The US president's Asia trip comes just over a year after he won election to the White House, and is designed to shore up US power in a region increasingly dominated by rising giant China.

But back home, Obama's bow in Japan seems to have grabbed much of the attention being paid to the trip.

The gesture appears to have touched a particularly raw nerve among Obama critics who said the president has hastened America's decline as a world superpower by being too apologetic and too deferential in his dealings with other world leaders.

While most of the commentary about the bow in Japan was decidedly negative, some political observers, like longtime Democratic activist Donna Brazile, came to the president's defense.

"I think it's a gesture of kindness," she told CNN, adding that the bow appeared intended to show "goodwill between two nations that respect each other."

Meanwhile, an unnamed, senior Obama administration official told the Politico.com news site that the president had simply been observing protocol.

"I think that those who try to politicize those things are just way, way, way off base," the official told Politico.

"I don't think anybody who was in Japan -- who saw his speech and the reaction to it, certainly those who witnessed his bilateral meetings there -- would say anything other than that he enhanced both the position and the status of the US, relative to Japan," Politico wrote.

"It was a good, positive visit at an important time, because there's a lot going on in Japan."

(with additional reporting)