A senior official with the US State Department says that they have been warning countries around the world, particularly US allies, to stop all purchases of Iranian oil. They say purchases must end by November, and the US is unlikely to offer any further exemptions to allow any more purchases.

“We are asking them to go to zero,” the official confirmed. He said China and India, two major customers of Iran, are among those the US has warned. The US withdrew from the Iran nuclear deal last month, and intends to again ban oil purchases.

Yet the Iran deal itself is still intact, without the US. China is even a signatory to that deal, and almost certainly won’t agree to stop buying Iranian oil just because the US tells them they can’t. This is doubly true because remaining signatories are trying to save the Iran deal.

Iran has reportedly already met with Chinese customers to ask them to keep buying oil, and while they haven’t gotten any guarantees, China appears to have plenty of justification to continue doing so. Iran has also requested EU nations commit to buying oil from them as part of a deal to remain in the nuclear pact.

For most nations, this will likely depend chiefly on the economic cost of ending Iran trade compared to what the US might do to them. So long as the nuclear deal remains in place, any US attempt to punish other countries will likely lead to a backlash, and limit the US ability to isolate anyone.