Iran has imposed no restrictions on U.S. oil firms willing to participate in energy projects in the country but American sanctions make such cooperation impossible, Iran’s deputy oil minister said on Monday.

“Iran has not imposed any restrictions on the U.S. companies, but they cannot participate in our (oil and gas) tenders due to the U.S. laws,” Amir Hossein Zamaninia, deputy oil minister for trade and international affairs, was quoted as saying by state news agency IRNA.

“Based on the U.S. Congress sanctions, the American oil companies cannot work in Iran,” he added.

Iran said on Saturday that it will hold the country’s first tender in mid-February since the lifting of international sanctions to develop oil and natural gas fields.

OPEC’s No. 3 oil producer hopes to draw foreign companies to invest in Iran and boost output after years of under-investment. However, foreign firms have so far made little inroads into the country despite the lifting of sanctions, according to Reuters.

President Donald Trump’s new U.S. administration on Friday imposed fresh sanctions on Iran, which it said were just initial steps. It said Washington would no longer turn a “blind eye” to Iran’s hostile actions.

Dismissing the new sanctions, Zamaninia said “such actions have had no effect, and international companies are still keen to do business with Iran.”

Anglo-Dutch oil firm Royal Dutch Shell signed a provisional deal in December to develop Iranian oil and gas fields South Azadegan, Yadavaran and Kish.