US military action against Iran appears to be back on the policy agenda in Washington amid the increasingly deadly crackdown on protesters in cities and towns across the country. Unconfirmed reports say that more than 500 people have been killed -- some rights groups say the death toll may be several times higher -- in suppressing the uprising, one of the biggest challenges to clerical rule since the 1979 Islamic Revolution. The demonstrations were sparked by spiraling inflation and a freefall of the currency, but have since turned into a broader…