Japanese lawmaker says Obama has the 'blood of slaves' -- and his comment instantly backfires
President Barack Obama reacts to Steve Kroft's assertion that Putin is challenging his leadership (Screen capture)

A Japanese lawmaker who said US President Barack Obama carried the "blood of ... slaves" was under pressure to explain himself Thursday after his remarks sparked uproar.

Kazuya Maruyama, a legislator from Prime Minister Shinzo Abe's ruling party, was attempting to highlight the dynamism of US society while speaking in parliament in Tokyo when he made the remarks, which instantly backfired.

"Now in the United States, a black man serves as president," Maruyama told lawmakers on Wednesday, adding that Obama "carries the blood of black people.

"This means slaves, to put it bluntly."

He then described as "unthinkable" at the time of the founding of the United States more than two centuries ago the idea that a black man could become president.

"It is a nation that transforms itself in dynamic ways," he concluded, praising the power of the country to change.

Obama is not a descendant of slaves but rather the son of a white mother from Kansas and a black Kenyan father who went to the US as a student.

Maruyama, when approached by reporters shortly after the parliament hearing, apologised and said he would ask for his remarks to be omitted from the official records.

He said he was trying to argue that Japan must learn from the United States and had not been aware of the tone of his comments, according to local media.

His clumsy effort to praise the US drew widespread condemnation and the fallout continued Thursday.

The remarks made national headlines and caused opposition lawmakers to submit a motion to the upper house of parliament pressing Maruyama to resign.

Chief Cabinet Secretary Yoshihide Suga, the government’s top spokesman, said that Maruyama "must fulfil his obligation to explain himself" in comments at a regular briefing.

The case served as the latest headache for Abe, who has seen a score of embarrassing scandals involving ruling party members.

Akira Amari, a key ally who served as the chief negotiator for the Trans-Pacific Partnership trade deal, left his ministerial post last month over a graft allegation published in a magazine.

And just last week, junior ruling party parliamentarian Kensuke Miyazaki, who had wanted to become the first national lawmaker to take paternity leave, announced he was resigning his seat after an affair with a bikini model while his wife, also a lawmaker, was pregnant.