AUSTIN, Texas -- Texas Gov. Rick Perry urged the U.S. attorney general to take action Wednesday against Americans who plan to take part in a pro-Palestinian protest by sailing to the Gaza Strip to challenge an Israeli naval blockade.

Perry wrote that he had information that American citizens were aboard two U.S.-flagged ships that plan to challenge the blockade on the Gaza Strip. He urged U.S. Attorney General Eric Holder to take legal steps to stop them from taking part, or to prosecute them if they make the attempt.

"The state of Israel is a friend and critical ally of the United States, and the only stable democracy in an increasingly unstable and hostile region," wrote Perry, a vocal supporter of Israel who is considering a run for president in 2012. "These initiatives to breach Israel's maritime blockade of the Gaza Strip is an unacceptable provocation."

Under federal law, anyone who "prepares a means for, or furnishes the money for, or takes part in, any military or naval expedition" against a friendly country can be fined or jailed for three years. Perry also suggested that Holder prosecute the protesters for providing materials or assistance to a terrorist organization.

Israel has enforced a Gaza border blockade since the Islamic militant group Hamas seized the territory in 2007. Last year, an Israeli raid on a similar flotilla killed nine activists on a Turkish vessel. Each side blamed the other for the violence.

Pro-Palestinian activists operating from Greece were preparing Wednesday to launch what are reported to be 10 ships carrying medical and construction supplies for Gaza sometime this week. Israeli Information Minister Yuli Edelstein called on organizers to deliver their cargo via an Israeli port, but the protesters rejected that option Wednesday.

Greece is the flotilla's base of operations, but activists won't disclose the exact location of the boats because of security concerns.

In his letter, Perry identified two of the ships as "The Audacity of Hope" and the "The Challenger II," both of which he said were registered in Delaware. Perry also wrote that the ships will depend on U.S.-based Inmarsat for communications and navigation, suggesting that the organization could be held responsible for the protesters' actions.

"I write to encourage you to aggressively pursue all available legal remedies to enjoin and prevent these illegal actions, and to prosecute any who may elect to engage in them in spite of your pre-emptive efforts," Perry wrote.

There was no immediate response from the Department of Justice. The State Department has warned Americans against participating in such a flotilla.