Lawmakers have debated adding border fees on carbon-intensive goods imported from developing nations should those nations not take action to reduce their own carbon emissions.

But the fees could be a headache for the U.S. government to administer, and it's uncertain that they would be allowed by global trade rules.

“You don't have to talk about tariffs yet,” Chu told the Reuters Washington Summit. “Let's figure out what the U.S. can and must do” to reduce greenhouse gas emissions.

Carbon tariffs have been supported by several U.S. senators, especially ones from manufacturing states that are hit hard by high unemployment. A plan for how the fees would work was included in the climate bill narrowly passed by the House of Representatives in June.

Under the House bill, tariffs on imports of energy-intensive goods like steel, glass, cement, and chemicals from China, India, and other countries would be triggered late in the next decade if the developing countries did not live up to promises of taking action on climate.

Several senators have supported such border fees as a guarantee they would not lose jobs and business in their home states to cheap imported goods.

Chu said to start off immediately considering tariffs “does no one good.”