A first military satellite named Noor is launched into orbit by Iran’s Revolutionary Guards Corps in an undisclosed location, Iran, April 22, 2020. Photo: Tasnim News Agency/Handout via REUTERS.

The United States has decided to end sanctions waivers allowing Russian, Chinese and European firms to continue work at certain Iranian nuclear sites, an American official and another source familiar with the matter said on Wednesday.

The decision, first reported by The Washington Post, seemed designed to tighten the “maximum pressure” policy Washington has applied since it pulled out of the Iran nuclear deal two years ago. That deal had provided Tehran with relief from economic sanctions in return for curbs on its nuclear program.

The sources, who spoke on condition of anonymity, said the move applied to waivers allowing international work at Iran‘s Arak heavy-water research reactor, the provision of enriched uranium for its Tehran Research Reactor and the transfer of spent and scrap reactor fuel abroad.

Those activities were designed to make the Iranian nuclear program less capable of producing weapons.

The sources said the US would give the companies 60 days to wind down their activities. They also said it would extend for 90 days a waiver allowing international support for the Russian-built nuclear reactor at Bushehr.

Alex Vatanka, an Iran expert at the Washington-based Middle East Institute think tank, said the Trump administration may have two motives for ending the waivers: looking tough to force Tehran to agree to even tighter restrictions on its nuclear program than in the 2015 deal and making it harder for any new U.S. administration to revive that agreement.

US President Donald Trump is running for re-election in November.

“The … point is to make (life) as hard as possible for whoever takes over from Trump, be that January 2021, or in four years time,” he added.