The European Commission has said it was putting forward a new list of US goods worth $84 billion that could be targeted by EU levies if tariff talks with Washington fail.
The bloc's trade chief, Commissioner Maros Sefcovic, announced the proposal, "accounting for some 72 billion euros' ($84 billion) worth of US imports", at a meeting with EU ministers in Brussels on Monday.
"We continue to engage with the US administration and prioritise a negotiated solution by the new deadline of August 1. I cannot imagine walking away without any effort," Sefcovic said before the meeting.
But the EU would have to prepare for all outcomes, he added, "including, if necessary, well-considered, proportionate countermeasures to restore the balance."
The move came after US President Donald Trump threw months of painstaking negotiations with the EU into disarray by threatening to impose tariffs of 30 percent on the bloc's goods if there is no deal by August 1.
'We should be ready'
EU trade ministers agreed they were still keen to secure an agreement with Washington before that deadline to head off the damaging duties.
But at the same time, Brussels is moving to ready potential retaliation if Trump presses ahead with the sweeping tariffs.
"There was a total unified position among the ministers that we should be ready to respond if needed," said Denmark's foreign minister, Lars Lokke Rasmussen, whose country holds the EU's rotating presidency.
The EU has already prepared a separate list of US imports worth $24 billion that it is ready to target with earlier tariffs from Trump on steel and aluminium.
The bloc announced on Sunday that it would further hold off putting that list into force as it searches for a deal with the United States by August.
