Strong support is expected today in Samoa's capital, Apia, for the Free Joe march.
The marchers intend walking from the Government Buildings to the US Embassy to deliver a petition calling for Cabinet Minister, Hans Joachim Keil, who has been detained in Missouri in the US, to be allowed to leave the country.
He is on bail on immigration charges - one of falsely and wilfully representing himself to be a US citizen, and one of attempting to use a US passport.
If convicted, he faces up to 15 years in jail.
Mr Keil's passport has been confiscated.
Co-organiser of the march, the president of the United States Veteran Association of Samoa, Mark Moors, says they've been inundated with support.
"Well basically it's called the Free Joe march. We realise, and we've told all those who are participating and supporters of the march, that this is not an anti-US march. This is a march in support of a citizen of the United States that's been persecuted incorrectly by the Department of Homeland Security and the Department of State."