Non-OPEC oil-producing nations struck a deal in Vienna on Saturday to cut crude output by 600,000 barrels a day, joining a pact meant to reduce a global oversupply of crude, lift prices and lend support to economies hurt by a two-year market slump.

The pact, the first between the two sides in 15 years, comes two weeks after OPEC agreed to reduce its own production by 1.2 million barrels a day.

If complied with, and that is a big “if” since many of the non-OPEC nations had previously expressly stated they would not actually cut but rather let oil production decline naturally, the deal would amount to a reduction of almost 2% in global oil supply and, as the WSJ notes, “would represent an unprecedented level of cooperation among oil-producing countries.”

Prior to today’s announcement, Russia had already announced it plans to reduce production by 300,000 barrels a day next year, down from a 30-year high last month of 11.2 million barrels a day. In a surprise move, Kazakhstan pledged a modest output cut after coming under strong diplomatic pressure, delegates said, Bloomberg noted. The International Energy Agency expected the Asian nation to boost production in 2017 by 160,000 barrels a day after a giant oilfield started pumping.

“I’m sure you are following the news about actual notifications to the customers by a number of countries notably Saudi Arabia,” Saudi Oil Minister Khalid Al-Falih said ahead of the meeting. “It should be a continuation of the positive spirit of cooperation and collaboration between OPEC and non-OPEC.”

Still, despite the trumpeted headline, there was little detail and it remains unclear whether the non-OPEC cuts include natural declines from countries such as Mexico, or consist entirely of genuine production cuts.”We managed to gather 25 countries from OPEC and non-OPEC with the idea of stabilizing the oil market and defending a fair price for our commodity,” Venezuelan Energy Minister Eulogio del Pino said before the meeting.