The U.S. State Department said on Friday that it has made a decision to extend sanction waivers on Iran's civil nuclear projects for 90 days.
The United States, which previous year withdrew from a 2015 Iran nuclear deal with world powers, has told buyers of Iranian oil to stop purchases by May 1 or face sanctions.
"We continue enriching", he said. "It is clear that over this period there has been a serious adaptation to this illegal trick by the United States", Tasmin News Agency quoted Russian Deputy Foreign Minister Sergei Ryabkov as saying.
The US State Department announced that it will toughen sanctions against Iran for expanding the Bushehr nuclear power plant. "We will also no longer permit the storage for Iran of heavy water it has produced in excess of current limits; any such heavy water must no longer be available to Iran in any fashion", US State Department spokesperson Morgan Ortagus said in a statement.
The European Union and foreign ministers of the three leading European powers, United Kingdom, France and Germany voices concern May 4 over the USA decision to end Iran oil import exemptions and two other exemptions related to its civilian nuclear program.
A senior parliamentarian called for talks with Iran's partners in the nuclear deal and the United Nations' International Atomic Energy Agency (IAEA) to ensure Iran could continue to enrich uranium, ISNA reported.
Facilities included in the waiver extensions include the Bushehr nuclear power plant, the Fordow enrichment facility, the Arak nuclear complex and the Tehran Research Reactor, the State Department said.
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The White House has ramped up pressure to reach a deal, warning it could still walk away from the months-long negotiations. The administration has repeatedly suggested that the negotiators are making progress.
The EU and the European powers also on May 4 said they took note "with regret and concern of the decision by the United States not to extend waivers with regards to trade in oil with Iran".
Meanwhile, Iranian President Hassan Rouhani said live on television on Saturday that Iran must counter U.S. sanctions by continuing to export its oil as well as boosting non-oil exports.
However, the United States did not renew two waivers.
The United States has tightened restrictions on Iran's nuclear programme by failing to renew two key sanctions waivers which allowed Russian Federation and the European nations to do business with Tehran, Aljazeera reported.
"No threat of new sanctions will stop our legitimate and mutually beneficial cooperation with Iran", he added.
"America is trying to decrease our foreign reserves".
"The remaining participants to the JCPOA are committed to working on the preservation and maintenance of financial channels and exports for Iran, together with third countries interested in supporting the JCPOA. We have no way but to resist and unite", Rouhani said in a televised speech on Saturday.