LONDON (Reuters) - Iran said on Monday that U.S. sanctions were impeding aid workers from sending helicopters to flood-hit regions of the country because of the poor state of the national helicopter fleet.

The country has announced an emergency situation in southern

provinces threatened by flooding and has evacuated dozens of villages as forecasters predicted more of the heavy rains that have killed more than 45 people.

Iranian Foreign Minister Mohammad Javad Zarif said in a tweet that U.S. sanctions were “impeding aid efforts by #IranianRedCrescent to all communities devastated by unprecedented floods.”

“Blocked equipment includes relief choppers: This isn’t just economic warfare; it’s economic TERRORISM.”

A deal with world powers on Tehran’s nuclear program in 2015 opened the way for Iranian airlines to update their fleets, but U.S President Donald Trump withdrew from that deal last year and reimposed sanctions on Iran.

Floods have affected at least 23 out of Iran’s 31 provinces since heavy downpours began on March 19. Western and southwestern parts of the country are expected to bear the brunt of the storms in the days ahead.

The commander of the army’s ground forces told state television that 20 of their helicopters were deployed to flooded areas to evacuate villagers.

Police renewed calls for people to avoid unnecessary journeys even though Iran is celebrating the Nowruz new year holiday, a time when many families travel.

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said last week that it was ready to offer help to Iran, but challenges caused by U.S. sanctions could affect the U.N. response.

Officials have said the government would compensate residents for flood damage.