Trump said on Tuesday that an Iranian attack on "anything American" would be met with great and overwhelming force, up to "obliteration."
"That statement indicates that US intentions are certainly illegal. The United States is not in a position to obliterate Iran, they do not have the capability other than using prohibited weapons to do this," Zarif said in an interview with CNN.
The Iranian minister also recalled that the threat of war was illegal under the United Nations Charter, stressing that Iran did not seek war.
The relationship between the United States and Iran has been progressively deteriorating since Trump unilaterally withdrew his country from the Iran nuclear deal last spring. Since then, in a succession of restrictive measures, Washington has put almost all major economy sectors of Iran under sanctions.
In May of this year, Iran said it would partially suspend its obligations under the nuclear deal.
Since then, the US-Iran strife has significantly escalated the security situation in the Middle East. The United States started building up its military presence in the region in what US National Security Advisor John Bolton called a clear message to Iran. According to the Pentagon, an aircraft carrier strike group, Patriot missiles, B-52 bombers and F-15 fighters were deployed to the region.