"No talks will be held with the Americans and the Americans will not dare take military action against us," Yadollah Javani, the IRGC's deputy head for political affairs, was quoted as saying by Tasnim news agency on Friday.
"Our nation ... sees America as unreliable."
The dismissal came amid rising tensions between Washington and Tehran.
Trump, who pulled the US out of a landmark deal curbing Iran's nuclear programme, has tightened sanctions on Tehran, eliminating waivers that had allowed some countries to buy Iranian oil, with the goal of reducing the country's crude exports to zero.
Last week, Washington deployed bombers and warships to the Middle East, citing "credible threats" from Iran. It did not offer evidence for the claim and Tehran dismissed the move as "psychological warfare".
The B-52 bombers arrived at a US airbase in Qatar on Thursday night, US Central Command (CENTCOM) said, while the carrier USS Abraham Lincoln passed through Egypt's Suez Canal on Thursday.
A day before Trump's offer for talks, Iran's President Hassan Rouhani said his country will resume some nuclear enrichment that had been halted under the 2015 accord.
Iran remains in compliance with the agreement but Rouhani threatened on Wednesday to do more if the remaining signatories to the pact - the United Kingdom, France, Germany, Russia and China - did not shield it from US sanctions.
Thousands of Iranians took part in marches on Friday to voice support for the government's move to scale back curbs on its nuclear programme.
Majid Takht Ravanchi, Iran's ambassador to the United Nations, said Washington's unilateral exit had eroded Tehran's trust.
"All of a sudden he decided to leave the negotiating table. ... What is the guarantee that he will not renege again?" Takht Ravanchi said in a US television interview on Thursday.
He dismissed US allegations of an Iranian threat as "fake intelligence" and said they were "being produced by the same people who in the run-up to the US invasion of Iraq did the same".