The text referred to a statement made by Khamenei on Twitter in December, according to a translation by Reuters, including the supreme leader's vow that the US would face retribution for the death of Qassem Soleimani.
Iranian Supreme Leader Ayatollah Ali Khamenei addresses the nation in a televised speech in Tehran. Photo / AP
Soleimani was one of Iran's top generals when he was killed in a US airstrike in Iraq last year.
"Those who ordered the murder of General Soleimani as well as those who carried this out should be punished. This revenge will certainly happen at the right time," Khamenei's statement read, according to Reuters.
Tensions between Iran and the US were high throughout Trump's four-year presidency but were at their worst when Soleimani was killed.
Donald Trump speaks with reporters as he walks to board Marine One on the South Lawn of the White House. Photo / AP
Despite the fraught relationship, Iran has pursued a relationship with Joe Biden since he entered the White House yesterday.
Iranian president Hassan Rouhani welcomed Joe Biden as the US president in a statement on Wednesday and called on the president to return the US to the nuclear deal negotiated in 2015 under the Obama administration.
