State Department Deputy Spokeswoman Marie Harf told the press Monday that Congress “shouldn’t take any steps” to exacerbate the “very delicate diplomatic situation” with Iran.

“This is the best chance we’ve had for a diplomatic resolution forever to the Iranian nuclear program. And who knows when we’ll get this chance again?” Harf said. “We need to give our team and our experts the space to get this done.”

Harf argued that the negotiations have made “concrete and tangible progress.” In response to a question on congressional intervention, Harf said that “no one should do anything that could possibly derail that process.”