Russia and China have released a joint statement reiterating the support for the landmark 2015 nuclear deal Iran made with major world powers.

The statement was released on Saturday at the Second Session of the Preparatory Committee for the 2020 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons.

In the statement both countries underlined their full support for the effective implementation of the United Nations Security Council approved Joint Comprehensive Plan of Action (JCPOA.)

They also stressed the independent role of the International Atomic Energy Agency (IAEA) in inspecting and monitoring Iran's nuclear activities.

The statement also emphasized the importance for all parties to the deal to thoroughly adhere to and fully implement their commitments under the nuclear accord.

US President Donald Trump, a long-time critic of the JCPOA, faces a May 12 deadline to decide whether to pull out of the agreement. Trump has repeatedly warned that he might ultimately terminate the agreement reached under his predecessor Barack Obama.

He said on January 12 that he wanted America's European allies to use the 120-day period before sanctions relief again came up for renewal to agree to tougher measures and new conditions; otherwise Washington would pull out of the deal.

Under the multilateral nuclear agreement, Iran undertook to put limits on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.

Other parties to the agreement have all criticized the US president's hostile views, saying the deal is sound and has proven to be functioning.