TEHRAN: Iran said a longstanding UN embargo on arms sales to and from the Islamic republic expired Sunday in line with a 2015 landmark nuclear deal with world powers from which Washington has withdrawn.

As Tehran celebrated, however, Washington argued that arms sales to Iran would still violate UN resolutions and threatened sanctions on anyone making such sales.

Iran has hailed the expiry as a diplomatic victory over its arch enemy the US, leaving the way open to purchase weapons from Russia, China and elsewhere.

"As of today, all restrictions on the transfer of arms, related activities and financial services to and from the Islamic Republic of Iran... are all automatically terminated," Iran's foreign ministry said in a statement.

The embargo on the sale of conventional arms to Iran was due to start expiring progressively from October 18 under the terms of the UN resolution that confirmed the 2015 nuclear deal between Tehran and world powers.

"As of today, the Islamic Republic may procure any necessary arms and equipment from any source without any legal restrictions, and solely based on its defensive needs," the ministry added in the statement on Twitter.

It insisted that under the terms of the nuclear deal, struck with the United States, China, Britain, France, Germany and Russia, "the lifting of arms restrictions and the travel ban were designed to be automatic with no other action required".

US President Donald Trump withdrew his country from the nuclear deal in 2018 and has unilaterally begun reimposing sanctions on Iran.