Donald Trump, the president of the United States, has warned Iran it "better be careful" after Tehran announced it would begin enriching uranium beyond a limit set in an international nuclear accord, reports Al Jazeera.

Trump last year unilaterally abandoned the 2015 deal and reinstated punishing sanctions on Iran, prompting it to announce in May a phased reduction of compliance with the landmark pact. 

On Sunday, Iran said it was hours away from passing the 3.67 percent uranium enrichment cap set in the deal, and threatened to keep reducing its commitments every 60 days unless the remaining signatories to the accord  - United Kingdom, Germany, France, Russia and China - protected it from US sanctions. 

It had already surpassed the uranium stockpile limit set in the accord on July 1.

When asked about the latest Iranian moves, Trump said on Sunday: "Iran better be careful because you enrich for one reason, and I won't tell you what that reason is, but it's no good." 

He did not elaborate on what actions Washington might consider, but told reporters that Tehran "will never have a nuclear weapon". Iran denies seeking nuclear weapons and refers to a religious decree issued in the early 2000s by Supreme Leader Ali Hosseini Khamenei that forbids "the production, stockpiling and use of weapons of mass destruction, and specifically nuclear arms".

Meanwhile, US Secretary of State Mike Pompeo threatened additional sanctions on Iran. 

In a Twitter post, he said: "Iran's latest expansion of its nuclear programme will lead to further isolation and sanctions." 

He added: "Nations should restore the long-standing standard of no enrichment for Iran's nuclear programme. Iran's regime, armed with nuclear weapons, would pose an even greater danger to the world."

Read more:

• Iran nuclear row - could U.N. sanctions return?

• Your threats can come back to bite you like nobody has been bitten before! - Trump blasted Iran