Tehran: Iran's supreme leader Ayatollah Ali Khamenei on Wednesday called the end of oil sanction waivers by the United States a "hostile measure" that "won't be left without a response".
"US efforts to boycott the sale of Iran's oil won't get them anywhere. We will export our oil as much as we need and we intend," his official English-language Twitter account said, quoting from a speech he delivered to workers in Tehran.
The United States announced on Monday it would halt the practice of exempting countries including India, China and Turkey from sanctions on purchases of Iranian oil.
In May last year, US President Donald Trump withdrew Washington from the 2015 Iran nuclear deal with world powers, which had given the Islamic republic sanctions relief in exchange for curbs on its nuclear programme.
Washington reimposed oil sanctions on Iran in November, but initially gave eight countries, including several US allies, six-month reprieves.
Five of the countries -- Greece, Italy, Japan, South Korea and Taiwan -- have already heavily reduced their purchases from Iran.
Iran has said the sanctions are "illegal".
"They (the US) wishfully think they have blocked Iran oil sales, but our vigorous nation and vigilant officials, if they work hard, will open many blockades," Khamenei said in the speech, partially aired on state TV.
"Enemies have repeatedly, in vain, taken action against our great nation (and our) revolution... but they must know Iranians won't give in," he added.
Khamenei, speaking in Tehran, also repeated his stance that Iran should move towards the sale of oil derivatives such as refined oil and petrochemical products instead of crude.
"I appreciate any decrease of dependency on this type of oil sales," he said.
Iran's foreign ministry said Monday that Iran "did not and does not attach any value or credibility to the waivers given to the sanctions." Iranian Foreign Minister
Mohammad Javad Zarif vowed on Tuesday that Iranians would not listen to Trump.
"Escalating #EconomicTERRORISM against Iranians exposes panic & desperation of US regime," he tweeted.
"Inheritors of ancient Persian civilisation don't base strategy on 'advice' of foreigners-let alone Americans."