Like some others in Congress who have suggested a military response to the alleged plot, Democratic Sen. Jeff Merkley of Oregon asked officials whether more serious measures were being considered. "Is it time to try something far more aggressive?" he asked, suggesting the possibility of placing blocks on Iranian tankers in the Persian Gulf until the country ceases its nuclear program.
"We have to be careful about the responses we make to any individual circumstances and that we don't escalate it beyond where it is," Sherman said. "We are certainly looking at all the options that might be available to us."