BRUSSELS (AP) — European Union leaders vented their frustration Friday at U.S. President Donald Trump's trade tactics, saying he is putting undue pressure on key allies by allowing barely a month of time to negotiate an exemption from punitive tariffs on steel and aluminum.

"It is a sort of gun to our head," Belgian Prime Minister Charles Michel said. "It is a strange way to negotiate with a partner."

The mood darkened at the table where the 28 EU leaders met for their summit when it became clear that the tariffs exemption for the EU would only last until May 1.

"The solution is not considered satisfactory," French President Emmanuel Macron said. He insisted Trump was taking the wrong approach to fighting dumping practices, in which countries overproduce a good and sell it on the market for very low prices. China has been singled out for dumping steel and aluminum on the global market.

"The U.S. strategy is a bad strategy," Macron said.

The United States and the EU are planning high-level talks to address trade imbalances which both sides see mainly being instigated by China. But instead of cooperation, the EU sees attempts Trump's move as divisive.

EU Commission President Jean-Claude Juncker said the five weeks was not enough to have coherent negotiations.

"It seems to me highly impossible to cover all the issues we have to discuss with our American partners from now to May 1 and we are asking a permanent exemption," he said.

Macron warned that if Trump does impose the tariffs, the EU stands ready to pounce.

"If we are attacked, we will react, showing no weakness. Everybody should realize this," Macron said.

The EU, the world biggest trading bloc, already has a list of U.S. goods to retaliate against that includes products from bourbon to jeans, motorcycles to orange juice. It seeks to hurt industries that are important to the Trump electorate.

Among the things that angers EU leaders most in the case is that Trump is citing national security as a reason for the tariffs, when Europeans say that they have shown strategic loyalty for decades.

The U.S. government is imposing tariffs of 25 percent on imported steel and 10 percent on aluminum. Besides the EU, Australia, Argentina, Brazil, South Korea, Canada and Mexico have also been given a temporary exemption.

The EU acknowledges that fundamental problems exist in the metals industry, but says there should be trans-Atlantic cooperation instead of competition, and certainly not hindered by the weight of temporary exemptions to trade sanctions.

"These discussions between allies and partners should not be subject to artificial deadlines," EU trade chief Cecilia Malmstrom said.

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Jill Lawless and Lorne Cook contributed to this report.