The U.S. and Iran escalated their war of words as a shaky ceasefire nears expiry, with each side raising the stakes ahead of a second attempt at reaching a peace deal.

Iran’s parliamentary speaker, Mohammad Bagher Ghalibaf, appeared to up the ante in a social media post on Tuesday, criticising U.S. President Donald Trump for “imposing a siege and violating the ceasefire,” and for seeking to turn the negotiation into “a table of surrender or to justify renewed warmongering.”

Ghalibaf also suggested that Iran is holding fresh leverage in the standoff. “In the past two weeks, we have prepared to reveal new cards on the battlefield,” Ghalibaf said, without elaborating. “We do not accept negotiations under the shadow of threats,” he added.

The sharpened rhetoric came after Trump renewed his threat of bombarding Iran with overwhelming military force if no deal is reached, saying that “lots of bombs [will] start going off.”

The status of further peace talks and other key details of the current relationship between the warring powers have grown increasingly opaque, with Trump vacillating between resuming saber-rattling rhetoric and indicating Washington’s readiness for additional negotiations with Iran.