WASHINGTON—Conservative U.S. Supreme Court justices on Wednesday signaled concern about allowing companies to be sued under American law for human rights abuses abroad in a case involving allegations that Arab Bank Plc helped finance militant attacks in Israel and the Palestinian territories.

Chief Justice John Roberts and Justice Samuel Alito, both conservatives, indicated that U.S. foreign policy tensions that could arise from such cases would be a reason to curb corporate liability. Conservative Justice Anthony Kennedy, who often casts the deciding vote in big cases, also appeared sympathetic to the bank’s arguments.

Their remarks during an hour of arguments in the case raised the possibility that the court, with a 5-4 conservative majority, could rule in favor of the Jordan-based bank in the lawsuit seeking to hold it financially liable for the attacks.

The court’s four liberals indicated that corporations should not be immune. Even if the court ruled in favor of the roughly 6,000 plaintiffs suing the bank, the lawsuit could still be dismissed on other grounds once it returns to lower courts.

The plaintiffs, appealing a lower court’s ruling blocking the suit, have accused the bank of being the “paymaster” behind attacks including suicide bombings because of its role in processing certain financial transactions. The plaintiffs include relatives of non-U.S. citizens killed in attacks and survivors of the incidents.

The plaintiffs said Arab Bank used its New York branch to transfer money that helped Hamas and other groups fund attacks and reward families of the perpetrators between 1995 and 2005.

The underlying legal question is whether corporations can be sued under a U.S. law called the Alien Tort Statute, which dates to 1789. In recent years, human rights lawyers have used it to seek damages against companies in U.S. courts for human rights violations abroad.

A ruling is due by the end of June.