Marine Gen. Joseph Dunford, the nation's top military officer, on Wednesday warned members of Congress that a 9/11 bill could hurt U.S. troops, including subjecting them to foreign courts.

In a letter obtained by The Hill, Dunford addressed his concerns about the Justice Against Supporters of Terrorism Act (JASTA), which would allow victims of terrorism to sue foreign governments.

ADVERTISEMENT

The letter comes hours before the Senate is expected to vote to override President Obama's veto of the legislation and follows one sent Tuesday by Defense Secretary Ash Carter, who warned the legislation could have "devastating" effects on troops.

"Any legislation that risks reciprocal treatment by foreign governments would increase the vulnerability of U.S. Service members to foreign legal action while acting in an official capacity," Dunford said in the letter to the leaders of the House Armed Services Committee.

He said, for example, U.S. troops supporting counterterrorism operations could be subjected to a foreign court's jurisdiction if it is alleged that they took actions that violated a foreign state's law.

Whether the final claims were proven to be with or without merit, troops would still be subjected to a foreign court's litigation process, he said.

In that process, U.S. troops could be held in civil or criminal contempt should they refuse to appear or otherwise comply with the foreign court's orders, he warned.

U.S. military property could also be at risk of being seized to satisfy monetary awards, he added.

And if a U.S. service member were sued, it would be up to a foreign court to decide whether classified or sensitive U.S government information would be part of the litigation process.

"This could put the United States in the position of choosing between the disclosure of classified or sensitive information, and subjecting a U.S. Service member to an adverse foreign court ruling," he said.

Lastly, Dunford said the bill could risk close security cooperation relationships between the U.S. and allies and partners.

"Any legislation that affects the long-standing principles of sovereignty should carefully consider any risks to the close security cooperation relationships between the United States and our allies and partners," he wrote.

The bill is backed by families of 9/11 victims who are seeking to file lawsuits against Saudi Arabia over those attacks.

Saudi Arabia is a long-standing U.S. military ally, but public sentiment has soured due to suspicions its government or members of its government supported the 9/11 hijackers.

Congress unanimously passed JASTA earlier this year, but President Obama vetoed the bill last week. The Senate has scheduled a vote to override the veto on Wednesday around noon.

Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D-Mo.) told reporters Tuesday she was undecided but that she was not concerned that U.S. troops would be dragged into foreign courts.

This story was updated at 10:42 p.m.