Iranian President Hassan Rouhani visits the Bushehr nuclearpower plant just outside of Bushehr, Iran, on Jan. 13, 2015. (Photo by Iranian Presidency Office)

MOSCOW, May 15 (Xinhua) -- U.S. pressure on Iran has forced Tehran to suspend the implementation of the Joint Comprehensive Plan of Action (JCPOA), known as the Iran nuclear deal, the Kremlin said Wednesday.

"We clearly understand that Iran makes these decisions not in an initiative, but responding to the pressure, which in general contradicts the letter and spirit of the JCPOA," Kremlin spokesman Dmitry Peskov told reporters.

"Here, unfortunately, the general concern remains," he said.

In recent weeks, Washington has ratcheted up pressure against Tehran with a series of sanctions, designations and military threats.

In response, Iranian President Hassan Rouhani announced last week his country's withdrawal from complying with the restrictions set by the JCPOA on Iran's enriched uranium reserves and heavy water supplies.

The United States, under President Donald Trump, withdrew from the Iran nuclear deal, which was endorsed by the United Nations Security Council and reached in 2015 between Iran, China, France, Russia, Britain, the United States, and Germany.