WATCH: White House economic advisor Brian Deese and press secretary Jen Psaki hold news briefing

White House press secretary Jen Psaki said the Biden administration is preparing fresh sanctions on Tehran should diplomacy in the nuclear talks fail and Iran’s “program continues to accelerate.”

Watch the briefing in the player above.

Negotiations between Iran and world powers aimed at salvaging a tattered 2015 nuclear deal resumed in Vienna Thursday, with tensions high after Tehran made demands last week that European countries strongly criticized.

Last week’s talks were the first in over five months, a gap caused by a new hard-line government assuming power in Tehran.

Speaking at the White House briefing, Psaki said the U.S. still believes “a diplomatic resolution offers the best path to avoiding a nuclear crisis.”

“However, given the ongoing advances in Iran’s nuclear program, the president has asked his team to be prepared in the event that diplomacy fails, and we must turn to other options and that requires preparations,” she said.

Psaki said the new actions would involve “additional measures,” on top of the already existing sanctions, “to further restrict Iran’s revenue producing sectors.”

She refused to lay out a specific timeline for any additional actions.

The United States has participated indirectly in the ongoing talks because it withdrew from the accord in 2018 under then-President Donald Trump. President Joe Biden has signaled that he wants to rejoin the deal.

Washington plans to send a delegation led by Robert Malley, the special U.S. envoy for Iran, to Vienna over the weekend.

The accord sealed in Vienna in 2015, formally known as the Joint Comprehensive Plan of Action, was meant to rein in Iran’s nuclear program in return for loosened economic sanctions.

Following the U.S. decision to withdraw and reimpose sanctions against Iran, Tehran has ramped up its nuclear program again by enriching uranium beyond the thresholds allowed in the agreement. Iran has also restricted monitors from the U.N. atomic watchdog from accessing its nuclear facilities, raising concerns about what the country is doing out of view.