Iran is determined to proceed with its defense program including missile development, the defense minister said.
"The Islamic Republic of Iran's right to self-defense is not negotiable and is among its red lines," Lieutenant General Hossein Dehqan was quoted by IRNA as saying on Friday.
"No force can limit the Islamic Republic of Iran's progress and development in the defense sector."
Dehqan's remarks came a day after receiving instructions in a letter from President Hassan Rouhani to expand the missile program, in response to US plans to impose new sanctions over a ballistic missile test Iran carried out in October.
"In line with the president's order, we will revise our [defense] program to increase the speed of and focus on [defense] activities," the defense chief said.
Under a landmark agreement clinched with major powers in July, Iran is putting in place the temporary curbs it accepted on its nuclear program in return for relief from international sanctions, expected within weeks.
On Wednesday, the Wall Street Journal, citing US officials, said President Barack Obama's administration is preparing to sanction nearly a dozen companies and individuals in Iran, Hong Kong and the United Arab Emirates for their role in developing Iran's ballistic-missile program.
The Journal later said White House has delayed imposing new sanctions.
The escalating dispute centers on the types of missile that Iran is allowed to develop and whether they are capable of, or designed to, carry nuclear warheads.
Greater Seriousness
"Apparently, the US government ... is considering adding new individuals and institutions to the list of its previous oppressive sanctions," Rouhani said in the letter, IRNA reported.
"It's necessary to continue with greater speed and seriousness the plan for production of various missiles needed by the armed forces within the approved defense policies," he wrote.
Rouhani added that the "development and production of Iran's ballistic missiles, which have not been designed to carry nuclear warheads, are important conventional instruments to defend the country and will continue."
US officials have claimed the Treasury Department retains a right under the nuclear deal, formally referred to as the Joint Comprehensive Plan of Action, to blacklist Iranian entities suspected of involvement in missile development.
Earlier on Thursday, Foreign Ministry spokesman Hossein Jaber Ansari condemned US plans to impose additional sanctions as "arbitrary and illegal".
"As [the Americans] themselves have previously acknowledged, Iran's missile issue has nothing to do with the action plan and cannot be used to deprive the Islamic Republic of its legitimate and legal right to boost its defense capabilities and [promote its] national interests," Jaber Ansari said, echoing Rouhani's letter.
A team of UN sanctions monitors claimed in a report on Dec. 15 that the Emad rocket tested by Iran in October was a ballistic missile capable of delivering a nuclear warhead, making it a violation of a UN Security Council resolution.
Ballistic tests by Iran are banned under Security Council Resolution 1929, which dates from 2010 and remains valid until the nuclear deal goes into force.
Once it does, Iran will still be "called upon" not to undertake any ballistic missiles work designed to deliver nuclear weapons for a period of up to eight years, according to a Security Council resolution adopted in July, right after the nuclear deal.
Iran says the resolution would ban only missiles "designed" to carry a nuclear warhead, not "capable of" carrying one, so it would not affect its military program as Tehran does not pursue nuclear weapons. Iran has called the Emad a conventional missile.
No JCPOA Breach
Abbas Araqchi, nuclear negotiator and head of Foreign Ministry's office for the JCPOA implementation, reiterated in an interview with state TV that the missile program is "clearly distinct" from the deal.
"In no way is the missile test a breach of the JCPOA."
