U.S. Trade Representative Robert Lighthizer says his office is preparing to impose tariffs on the $300 billion in Chinese products that aren’t already facing import taxes, another escalation in Washington’s dispute with Beijing.

The U.S. just after midnight Friday raised tariffs on $200 billion of Chinese imports to 25% from 10%. Hours later, an 11th round of U.S.-China talks ended without an agreement.

The tax hike brings to $250 billion the value of Chinese imports facing 25% tariffs. But about $300 billion in Chinese imports haven’t yet been hit in a yearlong dispute over China’s push to challenge American technological dominance, allegedly by stealing technology and forcing U.S. companies to hand over trade secrets.

Lighthizer’s office will have to get public comment before it can go ahead with the new tariffs.