Iran's supreme leader has ordered a purge of banking and finance officials in response to its economic crisis after the head of the judiciary said that the country was facing "economic war".
The Associated Press, meanwhile, reported that Khamenei said that negotiation "with the bullying and very eager government of the USA means giving it an instrument through which it can add to its hostility". Iran has denounced the sanctions as "US unilateralism". Trump reimposed the sanctions after pulling the United States out of an global accord that aims to curb Iran's nuclear programme.
Iran and the other signatories of the nuclear deal have said they intend to continue to abide by the agreement.
Ayatollah Khamenei's tweets followed a speech in Tehran, in which he described Mr. Trump's offer of talks as "a risky game" and his administration as a "bullying, fraudulent regime".
While E.U. nations have pledged to try to preserve economic ties with Iran, most large European companies already concede they will sacrifice trade with Iran, rather than risk suffering from secondary sanctions.
Khamenei, whose remarks on Monday come amid a sharp fall in the rial currency that has prompted angry protests, criticized the government of President Hassan Rouhani, a pragmatist cleric who championed the 2015 deal aimed at ending Iran's political and economic isolation.
Iran's rial currency has lost about half of its value since April in anticipation of the renewed United States sanctions, driven mainly by heavy demand for dollars among ordinary Iranians trying to protect their savings.
Iranian officials have blamed "enemies" for the fall of the currency and a rapid rise in the price of gold coins, and more than 60 people, including several officials, have been arrested on charges that carry the death penalty.
Also on Monday, Iran said it launched a production line for a radar-evading, short-range missile. He says Iran must change the way it operates, including its activities in Syria and Yemen.