Iran's atomic chief has warned that Tehran needs only five days to ramp up its uranium enrichment to 20 percent, a level at which the material could be used for a nuclear weapon.

The comments by Ali Akbar Salehi to Iranian state television on Tuesday followed repeated threats by US President Donald Trump to renegotiate or walk away from a historic 2015 nuclear deal.

"If there is a plan for a reaction and a challenge, we will definitely surprise them," said Salehi, who also serves as one of Rouhani's vice presidents.

"If we make the determination, we are able to resume 20 percent enrichment in at most five days."

WATCH: What's behind Trump's tough talk on Iran?

He added: "Definitely, we are not interested in such a thing happening. We have not achieved the deal easily to let it go so easily. We are committed to the deal, and we are loyal to it."

Iran gave up the majority of its stockpile of 20 percent enriched uranium as part of the nuclear deal it struck with world powers, co-signed by Trump's predecessor, President Barack Obama.

The 2015 accord, which lifted sanctions on Iran, currently caps the country's uranium enrichment at five percent.

Al Jazeera's Rosiland Jordan, reporting from the UN headquarters in New York, said there is "ongoing concern" among diplomats that further US actions to hold Iran accountable for "unrelated but still very serious violations" of international laws and Security Council resolutions "could end up ruining" the entire deal.

In recent weeks, Trump had already signed new sanctions imposing mandatory penalties on people involved in Iran's ballistic missile programme and anyone who does business with them.

The US legislation also applies "terrorism" sanctions to Iran's Islamic Revolutionary Guard Corps and enforces an existing arms embargo.

Our correspondent said the moves made the Iranians "very upset".

'Breakout time towards a bomb'

In response, Iranian President Hassan Rouhani warned last week that Tehran could ramp up its nuclear programme and quickly achieve a more advanced level if the US continues "threats and sanctions" against his country.

While Iran has long maintained its nuclear programme is for peaceful purposes, uranium enriched to 20 percent and above can be used in nuclear bombs.

As part of the 2015 deal, Iran processed its stockpile of near 20 percent uranium into a lower enrichment and turned some into fuel plates to power a research reactor and shipped the rest to Russia.

The Obama administration and most independent experts said at the time of the deal that Iran would need at least a year after abandoning the accord to have enough nuclear material to build a bomb.

Before the deal was struck, they said the timeframe for Iran to "break out" towards a bomb was a couple of months.

As part of the Trump administration's effort to push back against Iran, US ambassador to the United Nations Nikki Haley is heading to Vienna to meet UN monitors, and talk about whether Tehran is in full compliance with the nuclear deal, Al Jazeera's Rosiland Jordan reported.

"Her point is to try to go, and to not just hear from them but to also re-communicate the US concerns about Iran's intentions," our correspondent said.

While the economic benefits of the deal have yet to reach the average Iranian, it has paved the way for the reopening of the country's economy, while also boosting its oil production and sales.

Businesses have also started to sign multi-billion dollar deals with international companies, including Airbus and the US-based Boeing.

Analysts said abandoning the deal would also put those economic gains in jeopardy.