Iran said on Friday that Congresss decision to renew US sanctions for 10 years was a violation of last years nuclear agreement and promised an "appropriate" response.
"As repeatedly stated by high-ranking Iranian officials, the recent bill passed by the House of Representatives and the Senate to renew sanctions against Iran is against the (nuclear deal)," foreign ministry spokesman Bahram Ghasemi said.
The Iran Sanctions Act passed the Senate 99-0 on Thursday, after easily clearing the House of Representatives last month.
President Barack Obama is expected to sign the measure, a White House official said, adding that the administration does not believe the extension violates the nuclear deal.
The legislation does not directly address the nuclear pact. But some say the restrictions in the bill go against the spirit of the agreement, under which Tehran curbed its nuclear programme in exchange for sanctions relief from the United States and other nations.
The bill includes penalties against Iran's banking sector, as well as its energy and defence industries.
Senate Democrats Dianne Feinstein and Tim Kaine, who both backed the nuclear deal, said that while the president was currently waiving some sanctions as part of the agreement, "sanctions legislation must remain in place to allow an immediate snap-back" in the event of any violation by Iran.
Supreme leader Ayatollah Ali Khamenei said last month that he considered the sanctions bill a breach of the nuclear agreement and warned Iran would "react against it".
US President-elect Donald Trump heavily criticised the pact as he campaigned for the White House over the past year. Several fellow Republicans have called for its termination.