Russia dispatched one of its leading diplomats to Tehran this week to urge the Iranians to back off their threat to resume certain nuclear activities in retaliation for the US “maximum pressure” campaign.

Deputy Foreign Minister Sergey Ryabkov sat down for “a square talk” with his counterpart Abbas Araghchi, the Russian foreign minister said in a statement after the meeting. The Russian envoy sought to dissuade the Iranians from leaving the Non-Proliferation Treaty or following the Donald Trump administration in exiting the 2015 nuclear deal.

Why it matters: Russia appears to be playing an increasing role as a de facto mediator between the United States and Iran as the two countries inch closer to a regional confrontation.

On May 17, President Vladimir Putin said Russia was “not a firefighting squad to be saving this and that” — a colorful metaphor that disguised a multi-level message from the Russian leader to multiple parties. Now Ryabkov is telling both Tehran and Washington to show restraint in adopting measures that could “further complicate” the implementation of the nuclear deal, a sign that Moscow is nevertheless willing to play peacemaker.