US President Donald Trump is meeting with the European Commission President Ursula von der Leyen in Scotland on Sunday, as Brussels seeks to finalize a trade agreement with Washington before the August 1 deadline.
Ahead of the meeting, Trump gave "a good 50-50 chance" on Friday for a deal with the European Union to be reached.
Von der Leyen has been pushing hard for a trade pact that would see the bloc avoid the 30% tariffs that Trump has threatened on all goods from the EU.
Most EU goods already face a 10% tariff, with levies of 25% on cars and car parts and 50% on steel and aluminum.
On Sunday, US Commerce Secretary Howard Lutnick said the August 1 deadline was firm.
"No extensions, no more grace periods. Aug. 1, the tariffs are set, they'll go into place, Customs will start collecting the money and off we go," Lutnick told the US broadcaster Fox News.
Trump's tariff threats: Using trade as a weapon?
Will von der Leyen clinch a US-EU trade deal?
According to an EU diplomat briefed ahead of the meeting, set for 4:30 p.m. (1530 GMT), key issues still need to be hammered out.
"A political deal is on the table — but it needs the sign-off from Trump, who wants to negotiate this down to the very last moment," the diplomat told AFP.
European negotiators are aiming for a baseline levy of around 15 percent on EU exports to the US — the level secured by Japan.
Any deal will need to be approved by all member states. EU ambassadors, on a visit to Greenland, were updated on the negotiations by the Commission on Sunday morning, and would meet again after any agreement.
Edited by: Jenipher Camino Gonzalez