Amazon’s Prime Day is slamming into President Donald Trump’s trade war, with ever-shifting tariffs prompting some brands to sit out the summer sale and some shoppers dropping hints they plan to pull back.

Amid this growing threat, Amazon made crucial changes to its annual Prime Day sale, which started on July 8, to attract more customers. First, it extended the sales event to four days; last year it was only two days long. Amazon has also ramped up advertising of the event’s steep discounts.

A record $23.8 billion in sales is expected to be spent by consumers for Amazon Prime Days, Adobe said in a forecast released on July 7. That's a 28.4% increase year over year and $9.6 billion more than the comparable period last year. Last year, shoppers spent $14.2 billion during the two-day Amazon Prime event, according to Adobe.