American pro-Palestinian activists planning to join a flotilla attempting to challenge the blockade of Gaza have been warned by their government that they will be putting themselves in danger.

The flotilla, which is expected to include 36 Americans, is set to depart later this month. But the US State Department updated its travel advisory on Wednesday to say that they strongly urged citizens to "refrain from all travel to the Gaza Strip" by any means.

The Stet Department noted that Gaza, "including its border with Egypt and its seacoast, is dangerous and volatile" and said no attempts to travel there should be made "including via sea".

"US citizens participating in any effort to reach Gaza by sea should understand that they may face arrest, prosecution, and deportation by the Government of Israel."

The statement continued to stress that the US embassy in Tel Aviv and the US consulate general in Jerusalem would "not able to provide consular assistance in Gaza or on the high seas or coastal waters".

They warned anybody who planned to participate in the flotilla that they should both "be aware of the risks" and take note of announcements on travel to Gaza made by the Israeli Government.