The erratic tariff policies of the U.S. government are having a negative impact on global trade, said a Polish economics professor considering U.S. President Donald Trump's increase in a global tariff from 10 percent to 15 percent.

The U.S. Supreme Court ruled last Friday that the International Emergency Economic Powers Act does not grant the president the power to impose broad tariffs. In response, Trump announced a 10 percent tariff on all global imports on the same day. He followed up on Saturday by raising the rate to 15 percent.

"Confusion with all these tariffs is bad for business. It brings delays and uncertainty, while business likes certainty. Businessmen would like to see what are the new tariffs, what are the new rules. It's always bad if you don't know, because you cannot take decisions, because you don't know what should be the price with which you sell your things, your products, and for how much you can afford to pay for the products that you buy," said Tomasz Bielinski, adjunct professor in the Faculty of Economics at the University of Gdansk.

Bielinski said he believes that the European Parliament's suspension of the approval process for the EU-U.S. trade agreement is also a result of the uncertainty caused by U.S. tariff policies.

"European Union doesn't really know what will be the next move, and probably there's gonna be another tariff imposed by Donald Trump under the different law. So, European Union will have to act accordingly and negotiate a new deal or renegotiate an existing deal," he said.

According to the expert, the long-standing uncertainty in U.S. tariff policies is damaging the business environment, prompting many countries and regions to seek new partners.

"Other countries or other regions like European Union are planning to build other trade blocks, for example, between India and European Union, also the ties with Canada are strengthening, between European Union and Canada. European Union is looking for other partners to strengthen our relationships, because we don't really know what Donald Trump will do and what he's planning. So, there is a bit of uncertainty in nowadays geopolitical situation," Bielinski said.