President Trump’s administration has stepped up its sanctions on Iran and is offering a $15 million reward for information on its embargo-busting. It sent a special message to China during the announcement, warning it not to aid the rogue regime, which could foreshadow more economic skirmishes amid the trade war.

“We will sanction any sanctionable activity,” Brian Hook, the State Department’s special representative for Iran, told reporters Wednesday. “We've already done that once with China. So that is our policy. We have demonstrated that many times since we left the deal.”

Hook was responding to China’s reported decision this week to invest $280 billion in Iran’s oil industry in defiance of the sanctions that Trump’s team hopes will force Iran to agree to new curbs on its nuclear program and regional aggression. The pledge came as the administration unveiled sanctions on a major Iranian “oil-for-terror” network that generates funding for the elite Quds Force in Iran’s Islamic Revolutionary Guards Corps — in part from customers in China. Chinese oil trader Zhuhai Zhenrong and its chief executive were recently sanctioned for importing Iranian fuel.

“Vessels tied to the shipping network have tried to pass Iranian oil off as Iraqi oil. Countless Iranian vessels have gone dark just before delivering illicit cargo to places like Syria and to China,” Hook said. “Deception is at the heart of the Quds force shipping network. Every port operator, ship owner, and management company should steer clear of the targets identified today.”

That network, which includes at least 11 vessels that the Treasury Department blacklisted Wednesday, has smuggled roughly 10 million barrels of oil as U.S. sanctions intensified in recent months. Hook said that the operation was “largely” in support of Syrian dictator Bashar Assad, who relies on Iran and Iran’s biggest terror proxy, Hezbollah, for the ground forces that have preserved the Syrian regime through a bloody civil war. “These shipments sold for more than half a billion dollars,” Hook said.

The State Department on Wednesday also authorized a $15 million reward for information that helps investigators break other Revolutionary Guards smuggling networks, an unprecedented use of the Rewards for Justice program, which is devoted to thwarting terrorist plots, to target a government entity. The reward underscores the administration’s designation of the Revolutionary Guards as a terrorist organization in April.

Hook hinted repeatedly at punishments for Chinese companies that flout the Iran sanctions, but he simultaneously had to fend off questions about Trump’s apparent openness at the G-7 summit in France last month to easing pressure on the regime at the request of European allies. French President Emmanuel Macron, in keeping with Trump’s stated interest in granting Iran a “letter of credit,” wants the United States to waive sanctions if France extends a $15 billion credit line to the regime.

U.S. officials sought to dismiss that idea without getting crosswise with the president, who said in France he might be willing to allow Iran access to “some money to get them over a very rough patch” — even though the administration’s maximum pressure campaign is designed to create economic pressure.

“Obviously, the president is in close coordination with our partners and allies, listening to ideas, but we haven't seen anything yet that has any more prospect of becoming real than any other schemes that have been floated over the past year,” a senior administration official, speaking to reporters on condition of anonymity, told reporters Wednesday.

European allies have been trying to preserve the 2015 Iran nuclear deal that Trump withdrew the U.S. from last year. The credit line proposal comes in the wake of the regime stockpiling nuclear material at levels barred by the nuclear deal. Hook downplayed those differences as a mere “tactical disagreement” about how to deter Iranian threats while cautioning Europe not to fall for the regime’s “nuclear extortion” tactics.

“Iran never comes back to the negotiating table without diplomatic isolation, economic pressure, or the threat of military force — that’s just been the history of it,” he told reporters. “And so we will continue — as we have today — to deny the regime revenue, to drive up the costs of its malign behavior. And, we think that this creates the right atmosphere that will lead eventually to talks.”