Washington: A Republican congressman from Texas apologised Tuesday after he essentially compared US President Barack Obama to Adolf Hitler in a tweet about last week`s deadly attacks in France.

"Even Adolph (sic) Hitler thought it more important than Obama to get to Paris," Randy Weber posted on Twitter, after the US leader failed to join the more than a million people who marched through the French capital in an unprecedented show of defiance against Islamist extremism.

"For all the wrong reasons," Weber added, presumably referring to Hitler`s survey of German-occupied Paris in June 1940. "Obama couldn`t do it for right reasons."

The president was criticized for not participating in the massive unity rally or even sending a top emissary such as Secretary of State John Kerry to a march attended by several world leaders.

And the White House apologized for the mis-step.

But Weber`s caustic attack was seen as beyond the pale, and several Jewish groups reportedly demanded an apology.

"I need to first apologize to all those offended by my tweet," Weber said in a statement some 17 hours after his original post.

"It was not my intention to trivialize the Holocaust nor to compare the President to Adolf Hitler. The mention of Hitler was meant to represent the face of evil that still exists in the world today.

"I now realize that the use of Hitler invokes pain and emotional trauma for those affected by the atrocities of the Holocaust and victims of anti-Semitism and hate."

Other lawmakers including House Speaker John Boehner expressed their disapproval.

"The Speaker believes the tweet was inappropriate," Boehner aide Michael Steel told AFP.

House Democrat Nita Lowey called Weber`s Obama-Hitler comparison "disgraceful and severely unbecoming of a representative in the United States Congress."

This is not the first time Weber has used German symbolism in criticizing Obama.

Just before the president`s State of the Union address in January, 2014, the congressman tweeted, again with a spelling error: "On floor of house waitin on "Kommandant-In-Chef"... the Socialistic dictator.