BERLIN — U.S. special envoy for climate John Kerry said Tuesday that Washington is looking into the possibility of introducing a fee on imports from countries that don’t tax heavy polluters, but cautioned that such a move could carry risks “downstream.”

Kerry said President Joe Biden had instructed U.S. officials to examine “play it out: what are the consequences, how do you do the pricing, what is the impact.”

“But he wants to make sure we’ve thoroughly vetted it and thought about it as a matter of policy, particularly because our friends are doing so,” Kerry said.

The European Union has indicated it will put forward plans next month for a carbon border adjustment mechanism aimed at pushing its trading partners into doing more to cut carbon emissions if they want to sell their goods in the world’s largest single market.

The EU’s proposal, though still vague, has drawn significant concern, particularly from major emerging economies such as China, Brazil, India and South Africa.

Speaking to reporters in Berlin before talks with EU counterpart Frans Timmermans, Kerry said the Washington and Brussels had agreed to consult each other on the issue as they also push for greater international efforts to cut greenhouse gas emissions before U.N. climate talks in November.

“We want to make sure that it’s not going to have a counter impact, a negative impact on this process,” Kerry said.

“Nobody wants their businesses disadvantaged” by introducing carbon taxes that businesses elsewhere don’t pay, he said.

“But we do have some concerns about what the downstream impact might be, and we want to understand that fully before jumping on this,” Kerry added. “Our preference would be that every country is joining in in a fair manner in its efforts to reduce emissions sufficiently that we’re all paying the price of avoiding the consequences of the global climate crisis.”

“And so that includes obviously major emitting nations in the world. We all know who they are,” he said.