Iran's parliament speaker said Sunday that new US visa regulations amounted to "harassment" and reciprocal steps would be taken if the plans are implemented.
The rules, approved by Congress last month, would bar people from 38 mainly European countries from travelling to the United States without a visa if they have visited Iran, Iraq, Syria or Sudan since 2011.
Dual nationals of those countries would also be banned from using the Visa Waiver Program (VWP).
"Recently some US representatives have put some plans together which can only be referred to as harassment," parliament speaker Ali Larijani told lawmakers.
"If they don't amend it, there will be reciprocation from the Iranian side."
He did not specify what reciprocal measures might be taken. Iran recently simplified its visa entry rules, seeking to boost tourism, but the United States, Britain and Canada are among 11 countries whose citizens cannot obtain a visa on arrival.
The US plan came after calls from lawmakers and authorities to reduce security vulnerabilities after November's deadly jihadist attacks in Paris.
Some of the attackers were French and Belgians who could have travelled unrestricted to the United States.
Iran recently consulted with European countries and said the visa plan went against the spirit of the July 14 deal struck with world powers led by the United States over Tehran's nuclear programme.
The objective of the measures "is to harm the resolution of Iran's atomic dossier accomplished by Iran and the P5+1," Larijani said, referring to the countries that negotiated the deal -- the United States, Britain, China, France, Russia and Germany.
European diplomats have also warned of potential retaliation for the measures, arguing that the visa programme is based on reciprocity.
The president of the French Senate, Gerard Larcher, criticised the US plans on a visit to Tehran last month, saying they sent the "wrong signal" and undermined efforts to build confidence with Iran.
Those affected would not be barred from the United States but would be required to obtain a visa through standard means, which includes a face-to-face interview at a US consulate.
