The European Union’s trade chief is unsure what Washington wants in return for a permanent EU exemption from steel tariffs but she warned on Friday that she would resist pressure to cut EU duties on U.S. cars, Reuters reported.

European Trade Commissioner Cecilia Malmstrom, who will lead negotiations on behalf of the 28-state European Union, said it was not clear from her talks with U.S. counterparts this week what would satisfy the ultimate arbiter in the White House.

“That is what we need to work out,” she told Reuters in a telephone interview.

Trump has given the EU and six countries until May 1 to negotiate permanent exemptions from tariffs of 25 percent on steel and 10 percent on aluminium.

“These are things that would be mutually beneficial if we can solve, and we’re always willing to engage but we need to know what is the expected outcome for May and how serious is that deadline,” Malmstrom said.