By Daphne Psaledakis

WASHINGTON (Reuters) - The United States on Wednesday imposed sanctions on entities it accused of being involved in the illicit trade of Iranian petroleum and petrochemicals ahead of a new round of U.S.-Iran negotiations on Saturday, as Washington seeks to ramp up pressure on Tehran.

The U.S. State Department said in a statement it was imposing sanctions on seven entities based in the United Arab Emirates, Turkey and Iran that it accused of trading Iranian petroleum and petrochemical products. Two vessels were also targeted.

U.S. Secretary of State Marco Rubio said in a separate statement that the action targeted four sellers and one buyer of Iranian petrochemicals worth hundreds of millions of dollars.

Wednesday’s action is the latest move targeting Tehran since Trump restored his "maximum pressure" campaign on Iran, which includes efforts to drive its oil exports to zero and help prevent Tehran from developing a nuclear weapon.

"The President is committed to driving Iran’s illicit oil and petrochemical exports - including exports to China - to zero under his maximum pressure campaign," Rubio said.

Iran’s mission to the United Nations in New York did not immediately respond to a request for comment.

The action comes as the United States has relaunched talks with Iran over its nuclear program. U.S. and Iranian negotiators will reconvene in Rome on Saturday.

In his first 2017-2021 term, Trump withdrew the U.S. from a 2015 deal between Iran and world powers that placed strict limits on Tehran’s uranium enrichment activities in exchange for sanctions relief. Trump also reimposed sweeping U.S. sanctions.

Since then, Iran has far surpassed that deal’s limits on uranium enrichment.

Western powers accuse Iran of having a clandestine agenda to develop nuclear weapons capability by enriching uranium to a high level of fissile purity, above what they say is justifiable for a civilian atomic energy program. Tehran says its nuclear program is wholly for civilian power purposes.