Iran on Friday unveiled a new home-made long-range Multiple Independently Re-entry Vehicle (MIRV), named "Khorramshahr", during the nationwide military parades.
Though Iran has long boasted of having missiles in the same range in its arsenal, it was the first time that the Khoramshahr, with a range of 2,000km was displayed in public.
Iran said in its announcement on Saturday that the Khorramshahr missile could carry several warheads.
Iran has repeatedly stated its military capabilities are exclusively for defense purposes and they pose no threat to other countries.
Footage aired by the Islamic Republic of Iran Broadcasting (IRIB) on Friday showed the missile launched from an unknown location.
Previous Iranian missile launches have triggered USA sanctions and accusations that they violate the spirit of the 2015 nuclear deal between Tehran and major powers.
Rouhani also rejected USA accusations of Iran fomenting instability in the Middle East, including in Syria, Yemen, Iraq and Lebanon, and said Iran has historically assisted oppressed peoples.
If Washington walks out of the agreement, "any choice and any option" are open for Iran "that we see as beneficial to our country, " Rouhani said. "We will defend the downtrodden people of Yemen, Syria, and Palestine whether you like it or not", Rouhani added.
Trump has vowed repeatedly to take a tougher line toward Iran than his predecessor, threatening at various times to renegotiate or even dismantle the nuclear deal, and shoot Iranian boats out of the water if they provoke United States naval vessels in the Persian Gulf.
It also imposed sanctions on Iran after a ballistic missile test in January.
He has vowed repeatedly to take a tougher line towards Tehran than his predecessor, threatening at various times to renegotiate or even dismantle the nuclear deal, and shoot Iranian boats out of the water if they provoke U.S. naval vessels in the Persian Gulf.
He added that Iran remains fully committed to the pact, Press TV reported.The United States extended sanctions relief for Iran last week as part of the agreement, which Trump has described as "the worst deal ever".
Iran says it has no such plans.
Rouhani hit back at Trump's comments at the United Nations and condemned Israel for opposing the 2015 nuclear deal.
In Syria, Iran is a close ally of President Bashar Assad.
The Iranian armed forces remembered the 1980-1988 war between Iraq and Iran by holding a parade in which Iran's most advanced military power and abilities are showcased.
Trump has threatened to bin the nuclear agreement altogether, saying Iran is developing missiles that may be used to deliver a nuclear warhead when the deal's restrictions are lifted in 2025.