WASHINGTON (AFP) - In an America still scarred by the Sept 11, 2001 attacks, there has been an outpouring of support for France after the attack on satirical magazine Charlie Hebdo, with countless numbers brushing up rusty French to declare: "Je suis Charlie."

The wave of compassion across the media and online social networks as well as impromptu vigils in some US cities is all the more touching given that US-French ties have often frayed.

In 2003, the House of Representatives ordered that French fries in its canteen should be renamed freedom fries amid deep divisions over the invasion of Iraq.

And politicians who spoke French, like then senator John Kerry, were openly mocked, seen as pretentious and out of touch with ordinary Americans.

But Kerry, now the top US diplomat, was among Americans leading the wave of condemnation for the attack, which left 12 dead, among them some of France's best-loved and most famous satirical cartoonists.

"I want to speak directly to Parisians and all the French people to tell them that all Americans stand by their side," intoned Kerry, speaking in French.

France is America's oldest US ally, with the transatlantic partners having established diplomatic ties in 1776.

History books here still pay tribute to France's role in the young US nation's fight for independence, such as the American-French victory in the 1781 battle of Yorktown, which saw the British army routed.

"I would not have the freedom as an American if it was not for the help France gave us when we fought for our freedom at the beginning of our country," wrote one Virginian Thursday in an online condolence book opened by the French embassy in Washington.

"When France is attacked I feel America has been attacked... Je suis Charlie," the contributor added, one of several hundred people to leave messages on the site.

"Without your help throughout our shared history, I would not have the blessed life I lead here in the United States... Je Suis Charlie, and Je Suis Francaise," wrote another person identified only as J.

Yet another mourner said he recalled "a year of my boyhood spent in France... We are one with the French people in their grief, and tonight Nous Sommes Charlie."

And another person from Florida wrote the "bravery of the journalists and the Paris police will go down in history along with Napoleon, Lafayette, and the Revolution... I think my feelings are best conveyed by 'Vive La France'."

FRANCE'S SEPTEMBER 11

Senator Dick Durbin described the attack as France's September 11, when in 2001 Al-Qaeda militants riding hijacked planes brought down the World Trade Center in New York killing almost 3,000 people.

"A ce moment tragique, nous sommes tous Parisiens, nous sommes tous Francais," he said in French from the Senate floor. (At this tragic moment, we are all Parisians, we are all French.)

His words recalled the days after the 9/11 attacks when in a gesture of solidarity some French officials and media declared "Nous Sommes Tous Americains (We are all Americans)."

Hollywood stars and studios also lined up to express shock and sorrow at the Islamist attack, with two brothers suspected of being the gunmen still on the loose in northern France.

In a different tribute, the Nasdaq stock exchange changed its huge screen in Times Square, New York, to black emblazoned with the white words "Je Suis Charlie."

M Kerry and President Barack Obama both denounced Wednesday's cold-blooded shootings as an assault on freedom of speech and the press - values that are enshrined in the First Amendment of the US Constitution.

It is ironic therefore that a magazine like Charlie Hebdo, which gleefully pushes the boundaries of bad taste and vulgarity to lampoon everyone from the pope to French politicians, Christians and Muslims, has no equivalent in the more prudish America.

The closest example would be Mad magazine, known for its scatological and schoolboy humor, but which lacks the political bite of the French weekly.

US television comedy star and satirist Jon Stewart said late Wednesday that American hearts were with the staff of Charlie Hebdo.

"I know very few people go into comedy as an act of courage, mainly because it shouldn't have to be that ... but those guys were killed for their cartoons," Stewart said on his show.

"There is no sense to be made of this."