WASHINGTON (AP) — President Joe Biden used a White House event to mark Persian New Year on Monday to pay tribute to Iranian women and girls who took to the streets of Iran to protest following the death last year of 22-year-old Mahsa Amini and vowed to keep pressure on Tehran.

Biden said he wished the Nowruz holiday, a nearly 4,000-year-old tradition known as the Festival of Fire that’s linked to the Zoroastrian religion, would be a moment of “hope for the women of Iran fighting for their human rights and fundamental freedoms.”

“The United States stands with those brave women and all the citizens of Iran who are inspiring the world with their conviction,” Biden said, describing the reception as the biggest White House Nowruz celebration to date. “We’re going to continue to hold Iranian officials accountable for their attacks against their people.”

The United States, Europe and the United Kingdom have imposed a series of fresh sanctions on dozens of Iranian officials and organizations, including the country’s special military and police forces, for their violent clampdown.

The protests began in mid-September when Amini died after being arrested by Iran’s morality police for allegedly violating the Islamic Republic’s strict dress code.

The protests mark one of the biggest challenges to Iran’s theocracy since the 1979 revolution.