A demonstrator wears a similar T-shirt at a New York protest in July

Raed Jarrar said security officials warned him his clothing was offensive after he checked in for a JetBlue flight to California on 12 August.

Mr Jarrar said he was shocked such an action could be taken in the US.

US transport officials are conducting an inquiry after a complaint from the US Arab Anti-Discrimination Committee.

JetBlue said it was also investigating the incident but a spokeswoman said: "We're not clear exactly what happened."

'Authoritarian regimes'

Mr Jarrar's black cotton T-shirt bore the slogan in both Arabic and English.

He said he had cleared security at John F Kennedy airport for a flight back to his home in California when he was approached by two men who wanted to check his ID and boarding pass.

Mr Jarrar said he was told a number of passengers had complained about his T-shirt - apparently concerned at what the Arabic phrase meant - and asked him to remove it.

He refused, arguing that the slogan was not offensive and citing his constitutional rights to free expression.

Mr Jarrar later told a New York radio station: "I grew up and spent all my life living under authoritarian regimes and I know that these things happen.

"But I'm shocked that they happened to me here, in the US."

After a difficult exchange with airline staff, Mr Jarrar was persuaded to wear another T-shirt bought for him at the airport shop.

"We Will Not Be Silent" is a slogan adopted by opponents of the war in Iraq and other conflicts in the Middle East.

It derives from the White Rose dissident group which opposed Nazi rule in Germany.