TEHRAN: Iran's supreme leader Ayatollah Ali Khamenei said Tuesday that the Islamic republic will keep rolling back its commitments under the landmark 2015 nuclear deal.

"You did not carry out a single one (of your commitments), why do you want us to stick to our commitments?" Khamenei said, criticising European countries which are party to the deal.

"We have just started to decrease our commitments (in the deal) and this process will certainly continue," he said in a speech in Tehran partly aired on state television.

Iran-US tensions have soared since last year when President Donald Trump withdrew the United States from the hard-won 2015 nuclear deal and reimposed sanctions on the Islamic republic.

Angered that its beleaguered economy is not receiving sanctions relief it believes was promised under the deal, Iran has intensified its sensitive uranium enrichment work.

Iran announced last week that it had enriched uranium past the 3.67 percent limit set by the nuclear deal, and it has also surpassed the 300-kilogram cap on enriched uranium reserves.

European parties to the deal have called on Iran to return to its commitments under the deal.

On Sunday, President Hassan Rouhani said Iran had changed its strategy from one of "patience to that of retaliation".

"If they decrease then we too shall decrease our commitments (in the deal)... If they fully implement their commitments than we too shall fully implement ours," he said, quoted by the government website dolat.ir.

Tensions have since soared, with the US calling off air strikes against Iran at the last minute after Tehran downed an American drone, and Washington blaming Tehran for a series of attacks on tanker ships.

On July 4, British forces helped Gibraltar authorities detain an Iranian tanker which US officials said had been trying to deliver oil to Syria in violation of separate sets of EU and US sanctions -- claims denied by Iran.

In his speech on Tuesday, Khamenei vowed to retaliate against the British for the ship's seizure.

"The vicious British... have committed piracy and stolen our ship... God willing the Islamic republic will not leave these vicious acts unanswered," he said.