The United States has announced it is imposing sanctions on seven companies involved in the sale of Iranian oil, ratcheting up pressure despite new nuclear talks between Washington and Tehran, AFP reports.

The United States said it was targeting five commercial companies - four based in the United Arab Emirates and one in Turkey - that sell Iranian-origin petrochemical products to third countries, as well as two shipping firms.

"As Iran seeks to generate oil and petrochemical revenues to fund its destabilizing activities and support its terrorist activities and its proxies, the United States will take steps to hold both Iran and all of its partners involved in sanctions evasion accountable," said Secretary of State Marco Rubio.

The move comes just after Iran announced a fourth round of talks with President Donald Trump's administration to be held on May 3 in Rome.

Iran is seeking sanctions relief as part of a deal on its disputed nuclear programme.

Trump's business friend and globe-trotting envoy Steve Whitkoff is leading the talks and expressing optimism of a deal as Trump seeks to avoid an Israeli strike on Iranian nuclear sites.

During his first term, Trump scrapped an earlier agreement with Iran negotiated by former President Barack Obama and Washington's European allies.

He imposed wide-ranging sanctions, including trying to ban Iran from selling oil to all other countries - with China the key market.

The sanctions remain in place, although levels of enforcement vary. | BGNES