WASHINGTON (AFP) - The White House admitted on Monday it should have sent a higher-ranking representative to the massive weekend march against terrorism in Paris, which was attended by many world leaders.

"We should have sent someone with a higher profile to be there," White House press secretary Josh Earnest said. Washington was represented at the event by the US ambassador to France, Ms Jane Hartley.

Mr Earnest said President Barack Obama would have liked to have gone himself, but suggested that the security requirements and short planning time had prevented it.

"The security requirements around a presidential level visitor or even a vice-president-level visitor are onerous and significant," he said. "In a situation like this, they have a pretty significant impact on the other citizens who are trying to participate in a large public event like this."

About 1.5 million people flooded the streets of the French capital Sunday to memorialise the 17 people killed in attacks in Paris that began last week with a massacre at a satirical weekly and ended with a hostage standoff at a kosher grocery.

French President Francois Hollande was joined at the march by 50 world leaders, including the Israeli prime minister and the Palestinian president, in a display of unity that made headlines worldwide.

Yet the failure of Mr Obama, his deputy Joe Biden or a senior Cabinet official to join the rally angered many US commentators. Many accused Mr Obama of letting down ally France.

Secretary of State John Kerry said he would travel to Paris after wrapping up his tour of South Asia.

Adding to the dismay among some American pundits and lawmakers, US Attorney-General Eric Holder had been in Paris for a meeting on terrorism, but even he did not join the rally.

CNN journalist Jake Tapper, one of the television news channel's main anchors covering the attacks in Paris, spoke of his "shame" at the lack of high-ranking US representation.

"I say this as an American - not as a journalist, not as a representative of CNN - but as an American: I was ashamed," Mr Tapper wrote in a blog on CNN's website.

The New York Daily News tabloid issued a blunter indictment of the no-show in a front-page headline addressed to American officials: "You let the world down."

US officials pointed out that Mr Kerry was on a long-standing trip to India that made it impossible to attend.

Washington officials note that the security circus surrounding any trip by a US president or vice-president may have risked deflecting attention away from the spirit of Sunday's occasion.

"For once this is not about us," a US official said.

Yet the explanations failed to stem the tide of criticism, particularly from Mr Obama's Republican foes.

"Our president should have been there, because we must never hesitate to stand with our allies," said Republican Ted Cruz.

Mr Marco Rubio, who like Mr Cruz is seen as a possible Republican challenger for the White House in 2016, also criticized the absence, but said he understood the argument that presidential security may have been disruptive.

"I thought it was a mistake not to send someone," Mr Rubio said. "There are a plethora of people they could have sent. I think in hindsight, I would hope that they would do it differently."

Privately, French officials played down the alleged snub, and the French embassy in Washington insisted that Paris was fully satisfied by their ally's response.

The president's top counterterrorism adviser Lisa Monaco met with French Ambassador Gerard Araud, who "thanked Ms Monaco for unwavering US support to France in the aftermath of the attacks," as the two discussed the French investigation and reviewed US intelligence, the White House said.

A mission spokesman told AFP that "as far as the reactions of the US authorities are concerned, we have been overwhelmed and very moved by them since the beginning of the crisis".

He thanked the United States for "numerous public statements by President Obama, Secretary Kerry (in French!), multiple phone calls at the highest level and, of course, the signature of our condolence book here at the embassy by the President."

Despite the relatively low-level US representation, Mr Earnest said: "There should not be and is not any doubt in the minds of the people in France or people around the world and certainly not among our enemies about how committed to a strong relationship that the United States is with France."