Iran's missile programme is "non-negotiable" and tests will continue, foreign ministry spokesman Bahram Ghasemi said on Tuesday, following criticism from European Union diplomats.
"Iran's defence capabilities cannot be compromised and are under no circumstance negotiable," he told state television IRIB.
"Missile tests are conducted within the framework of Iran's defence policies."
A meeting of EU foreign ministers in Brussels on Monday urged Tehran to refrain from ballistic missile testing.
Iran's military has carried out a number of missile tests in recent months, which the United States and European governments have said are a breach of its commitments under last year's nuclear deal.
Western powers say the missiles are capable of carrying nuclear warheads and therefore go against the deal, under which Iran agreed to curb its nuclear programme in exchange for a lifting of global sanctions.
The EU foreign ministers called on all sides to respect the agreement -- reflecting concerns over US president-elect Donald Trump's vow to ditch it.
Ghasemi welcomed the EU's "interest and determination to develop ties with the Islamic Republic of Iran and the renewed emphasis on the commitment of this union in the full implementation by all sides" of the nuclear deal.
The EU has been pushing to open an office in Tehran amid a surge in interest from European companies hoping to resume trade ties.
But there has been push-back from Iranian conservatives, who say the office would be used to press human rights issues, and Ghasemi said last week it was "unlikely such an office would be opened... in the short term".
The head of Iran's Human Rights Council, which falls under the hardline judiciary, said last month: "If this office is used for following up trade issues, there is no problem. But they have said that following the opening of this office, they want to have close contacts with human rights defenders and NGOs.
"So they should know that the judiciary will definitely not allow such a den of corruption to be established inside Iran," he said, according to the ISNA news agency.