Paris (AFP) - US civil rights leader Jesse Jackson voiced "disgust" Wednesday at the ideas of French far-right veteran Jean-Marie Le Pen, after the surprise revelation that they had dined together in Paris.

The pair traded tense Twitter posts after the National Front firebrand posted a picture of them at a restaurant in the French capital at the weekend.

"I did not know him, I've never met with him before, and I find his ideas xenophobic and repulsive," Jackson told AFP, seeking to explain what he said was an inadvertent encounter.

Le Pen and his wife Jany "were invited by the other hosts at the dinner. It was not at all a political meeting," said Jackson, in France for events commemorating the abolition of slavery.

Le Pen tweeted a first photo of the two men at a Moroccan restaurant, along with a note apparently handwritten by Jackson reading: "May 8-'16. Jean-Marie, (wife) Jany Le Pen, Keep Hope Alive, Continue".

"Keep Hope Alive" was a catchphrase Jackson used during his unsuccessful 1988 bid for the US presidency.

Jackson responded with a tweet two hours later saying: "Did not know you were coming to dinner. Never met you before. Do not share your beliefs."

The 87-year-old co-founder of the National Front party followed up with another picture in which a smiling Jackson is sitting at a table between him and his wife.

It was accompanied by the tweet: "Attention media who speak of 'imagined dinner'", with the hashtag #desinformation" -- French for disinformation.

Jackson, 74, speaking on the sidelines of a meeting with entrepreneurs, said: "If I had known he was who he is, I would have left out of my disgust with some of his policies... I find the ideas of xenophobia and anti-Semitism repugnant and very unhelpful to making a peaceful world."

He said he felt "betrayed" at the portrayal of the dinner Sunday "as if it were a stage for some relationship", adding: "Those who tweeted out the meeting... deceived me".

Jackson added: "My preoccupation was with the slavery commemoration."

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The Baptist minister attended events on Tuesday alongside French President Francois Hollande and Prime Minister Manuel Valls marking France's slavery remembrance day.

He laid a wreath at the tomb of Victor Schoelcher, who led France's abolitionist movement.

- 'There was no trap' -

An aide to Le Pen told AFP that Jackson "knew he was going to dinner with Jean-Marie Le Pen and who he was."

He added: "There was no trap, and there was even an agreement with their mutual Moroccan friends that the dinner was not private. The photos were taken by a professional photographer."

Le Pen was kicked out of the anti-immigration FN for refusing to tone down racist and anti-Semitic comments.

His estranged daughter Marine Le Pen has since presided over an unprecedented rise in the party's fortunes, with many pollsters predicting the FN will make it to the second round of the presidential election next year.

Her father managed this feat in 2002, coming in second ahead of Socialist Lionel Jospin before losing to the conservative Jacques Chirac.

The Le Pen aide said Jackson "was often accused of anti-Semitism, accusations that he shares with Mr Le Pen. Maybe his entourage is worried" over the publicity from the dinner.

Jackson was criticised in the early 1980s for his ties to black nationalist leader Louis Farrakhan, known for his anti-Jewish rhetoric.

He also apologised in a speech before national Jewish leaders for using a pejorative term for Jews in remarks to a Washington Post reporter in 1984.

Le Pen was fined 30,000 euros ($34,000) last month for repeating his view that the Nazi gas chambers were a "detail" of history.