"Some nonpartisan experts on Iran and on US policy in the Middle East say Iran appears to be pursuing a provocative but calibrated strategy to counter what they see as a potentially existential American threat — as severe economic sanctions strangle the economy and cut off vital oil revenues — as well as to preserve the nuclear agreement. Thus, US has closed off other avenues for responding, Iran is falling back on tactics associated with its reputation as a rogue state, including asymmetric military escalation, nuclear blackmail and threatening oil shipments, though Iran denies American accusations that it attacked tankers last week, or the downing of an American drone ."