Iran celebrates its National Nuclear Technology Day, with President Hassan Rouhani warning US President Donald Trump against a possible pullout from the nuclear deal with the Islamic Republic.

"If the deal breaks, they will surely regret it. They will witness the fallout in less than a week," Rouhani said on Monday during a special ceremony held in commemoration of the occasion.

Spokesman of the Atomic Energy Organization of Iran (AEOI) Behrouz Kamalvandi said Iran can resume uranium enrichment to the 20% purity level which the country halted under the nuclear deal, only within two days.

Trump has threatened to walk away from the nuclear deal and reimpose sanctions by May 12 unless tough new restrictions are imposed on Iran's nuclear and missile programs.

US sanctions that were lifted under the Joint Comprehensive Plan of Action (JCPOA) of 2015 will resume unless Trump waives them again.

Rouhani said, "Iran will not violate the nuclear deal, but if the United States withdraws from the deal, they will surely regret it. Our response will be stronger than what they imagine and they would see that within a week."

"Whether the JCPOA exists or not, with or without the US, we are prepared for whatever circumstances and have plans [for any eventuality]," he added.

On Monday, Iran unveiled its latest nuclear achievements including a nuclear battery and centrifuges for the oil industry. Rouhani observed 84 achievements in the areas of centrifuge technology, nuclear fission, nuclear medicine, and power plants put on display in Tehran.

The president said the Fordow enrichment center in central Iran was to host inauguration of new facilities, and that nuclear research would gather more pace.

Iran's President Hassan Rouhani observes the country's nuclear achievements on the 12th National Nuclear Technology Day in Tehran, April 9, 2018. (Photo by president.ir)

AEOI head Ali Akbar Salehi said Iran had also transferred the first yellowcake consignment from Saghand uranium mine in the central Yazd Province to the uranium conversion facility (UFC) in Isfahan.

The country had also broken the ground on creating two more units at its Bushehr Nuclear Power Plant in the south over the past year, he said.

Since the nuclear deal went into effect in early 2016, Iran has imported around 400 tonnes of yellowcake - a type of uranium condensate powder - and sold enriched uranium to a number of countries, including the US.

Salehi reiterated Iran's commitment to the JCPOA, as verified by the United Nations nuclear agency on 10 occasions. However, if the other sides chose to act against the agreement, Tehran would act to preserve its interests, he added.

Trump "who has big claims and many ups and downs in his words and actions has been trying for 15 months to break the JCPOA ... but the structure of the JCPOA is so strong that it has not been shaken by such quakes," Rouhani said.

"Even if one day (the US) harms the JCPOA, we will be the winner in the public opinion of the world as the nation that stuck by its commitments," the president said.

"If they withdraw, it would mean that they are not committed to their words," he added.

Trump wants Iran's missile capabilities to come under the provisions of the nuclear agreement, which Tehran vehemently rejects.

Rouhani said on Monday that Iran’s missile capabilities are purely defensive.

"We will produce any weapons necessary to defend our country in such a volatile region. But we will not use our weapons against our neighbors," he said.

The president said some parties want Iran to be subservient and bow to their demands without regard for its own interests.

Iran, he said, will never try to satisfy the whims of the "ill-wishers", but will continue down the path of obtaining scientific technology.