Khamenei said Iran could start ramping up its nuclear activity, which it agreed to limit in 2015 in exchange for sanctions relief, if the accord no longer benefits the country.
He warned that if the Europeans do not meet these demands, Iran would resume its enrichment of uranium, which was shelved under the deal to minimize the risk of Tehran developing nuclear weapons.
The Western European signatories to the Iran nuclear deal have until next Friday to provide Tehran with concrete proposals to offset the consequences of the U.S. decision to pull out of the Joint Comprehensive Plan of Action (JCPOA), a senior Iranian official said.
Trump denounced the accord, completed under his predecessor Barack Obama, because it did not cover Iran's ballistic missile programme, its role in Middle East conflicts or what happens after the deal begins to expire in 2025.
Secretary of State Mike Pompeo issued a 12-point list on Monday calling on Iran to heed US demands that include abandoning uranium enrichment and shutting down its missile program. But that has proven hard, with European companies frightened away by United States sanctions.
"We expect the (economic) package to be given to us by the end of May", the official noted, according to Reuters.
"The meeting will offer an opportunity to review the implications of the withdrawal of the United States from the JCPOA and discuss the way forward to ensure the continued implementation of the deal in all its aspects", the European Union said ahead of the deal.
British, Chinese, French, German and Russian officials will try to flesh out with Iran's deputy foreign minister a strategy to save the deal by keeping oil and investment flowing, while circumventing USA sanctions that risk hurting the economy.
"I think we have good reasons to think we will succeed, provided that, once again, all of us have relevant political will", said Mikhail Ulyanov, head of the Russian Foreign Ministry's arms control and non-proliferation department.
"European banks should safeguard trade with the Islamic Republic", Khamenei said.
The International Atomic Energy Agency, which polices the pact, said Thursday that Iran continued to comply with its terms, but could be faster in allowing snap inspections.
"We are working on a variety of measures to mitigate consequences of the U.S. withdrawal", the official, who did not want to be named, said while cautioning that "there are things that will take more time".
New U.S. sanctions are being phased in, but already many non-U.S. companies have said that they will also likely have curtail operations in Iran for fear of losing access to the much more important American market. He also rejected any new negotiations over Iran's missile program, which was not covered in the nuclear deal. "We made the JCPOA in good faith and we remained committed to the JCPOA and they just pulled out.so name me a single reason why we should enter into a new negotiation with the USA or a new deal?" The IAEA's director general, Yukiya Amano, briefed participants before Friday's meeting.