United Against Nuclear Iran said in a letter to Eni that it wanted proof the company was working to cut its ties with Iran.
UANI was part of a group protesting in New York against companies that do business with Iran.
Eni officials in a statement to UANI said they were working to wind down their activity in the Iranian energy sector.
"To my knowledge, Eni has assured the U.S. administration that it has taken significant verifiable steps toward stopping its energy-related activities in Iran and will not engage in any such activities in the future," said Enzo Viscusi, a senior adviser from Eni, said in a statement to protesters. "We note that Italy is cooperating fully with multilateral sanctions efforts with respect to Iran."
Eni in 2010 purchased around $2 billion of Iranian crude oil. The U.S. State Department said in late 2010 that BP and Shell were no longer selling jet fuel to Iran Air, while Shell, Total, Spanish energy company Repsol and Italy's Eni all abandoned work in the upstream sector.
UANI said it wants written proof by Monday that Eni is ending its business and investment activities in Iran.