Missiles are displayed as Iranian President Hassan Rouhani attends an armed forces parade in Tehran, Iran, September 22, 2017. President.ir/Handout via REUTERS

Iran said on Saturday it had successfully tested a new ballistic missile with a range of 2,000 km (1,200 miles) and would keep developing its arsenal despite U.S. pressure to stop.

The United States has imposed unilateral sanctions on Iran, saying its missile tests violate a U.N. resolution, which calls on Tehran not to undertake activities related to missiles capable of delivering nuclear weapons. Iran says it has no such plans.

U.S. President Donald Trump said on Twitter the missile test illustrates the weakness of the Iran nuclear deal reached by his predecessor Barack Obama. He also linked the action to recent aggressive moves by North Korea.

"Iran just test-fired a Ballistic Missile capable of reaching Israel. They are also working with North Korea," Trump said on Twitter. "Not much of an agreement we have!"

Iran said in its announcement on Saturday that the Khorramshahr missile could carry several warheads.

State broadcaster IRIB carried footage of the missile test without giving its time or location. It included video from an on-board camera which it said showed the detachment of the cone that carries multiple warheads.

"You are seeing images of the successful test of the Khorramshahr ballistic missile with a range of 2,000 km, the latest missile of our country," state television said, adding this was Iran's third missile with such a range.

The Khorramshahr was first displayed at a military parade on Friday, where President Hassan Rouhani said Iran would strengthen its missile capabilities.

Britain voiced concerns about the latest test.

"Extremely concerned by reports of Iran missile test, which is inconsistent with UN resolution 2231. Call on Iran to halt provocative acts," British Foreign Secretary Boris Johnson wrote on Twitter.

France also said it was extremely concerned and called on U.N. Secretary-General Antonio Guterres to carry out a full report on the launch.

"France asks that Iran cease all destabilizing activity in the region," Foreign ministry spokeswoman Agnes Romatet-Espagne said in a statement. "(France) will consider with its partners, notably European, the means to obtain from Iran the cessation of its destabilizing ballistic activities."

Iranian President Hassan Rouhani arrives to attend an armed forces parade in Tehran, Iran, September 22, 2017. President.ir/Handout via REUTERS

Trump told the U.N. General Assembly on Tuesday that Iran was building its missile capability and accused it of exporting violence to Yemen, Syria and other parts of the Middle East.

He also criticized a 2015 pact that the United States and other world powers struck with Iran under which Tehran agreed to restrict its nuclear program in return for relief from economic sanctions.

Iran's defense minister said on Saturday foreign pressures would not affect Iran's missile program.

"On the path to improve our country's defensive capacity we will certainly not be the least affected by any threats and we won't ask anyone's permission," Brigadier General Amir Hatami said in remarks carried by state television.

Iran denies its missile development breaches the U.N. resolution and says its missiles are not designed to carry nuclear weapons.

"The weight of the Khorramshahr missile's warhead has been announced to be 1,800 kg (4,000 lbs), ... making it Iran's most powerful missile for defense and retaliation against any aggressive enemy," state television said.