He described the approach as "a one-two punch," combining a blockade with sanctions. No list of designated targets or effective dates was released.

He also called for Chinese cooperation, arguing that China draws a large share of its energy from the Gulf and that reopening the Strait of Hormuz and easing energy prices would serve Chinese interests.

Asked whether the United States might target China over business with Iran, he said many conversations are better held in private, neither confirming nor denying.

China's foreign ministry, asked at a regular briefing about the effect on China of the US president's economic threats toward Iran, restated its standing opposition to unilateral sanctions.

Because a large share of Iran's seaborne crude exports has gone to China, discussion of whether sanctions bite cannot easily be separated from China's response.

Energy prices are the variable most directly linked to consumer prices in this episode, on the same axis as the fuel costs cited in American retail results.

The substance of the sanctions must await next week's announcement. What has been made public so far is a statement of direction.