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.

The breakdown in proposed reduction by non-OPEC country is as follows:

• Azerbaijan to cut 35,000 barrels a day
• Bahrain to cut 12,000 barrels a day
• Bolivia to cut 4,000 barrels a day
• Brunei to cut 7,000 barrels a day
• Equatorial Guinea to cut 12,000 barrels a day
• Kazakhstan to cut 50,000 barrels a day
• Malaysia to cut 35,000 barrels a day
• Mexico to cut 100,000 barrels a day
• Oman to cut 45,000 barrels a day
• Russia to cut 300,000 barrels a day
• Sudan to cut 4,000 barrels a day
• South Sudan to cut 8,000 barrels a day

Indonesia, which until recently was an OPEC member (having returned in 2015) but mysteriously was suspended from the cartel during the November Vienna meeting, did not figure in the negotiations.

As the WSJ notes, representatives from a number of countries met Saturday morning for a breakfast and then headed to OPEC’s headquarters in central Vienna where they hashed out an agreement.

Securing a coalition beyond their own cartel has become important for OPEC officials as the rise of American oil producers has put them on the defensive. OPEC worries that any increase in oil prices following a cut in production will eventually lead U.S. output to flood back into the market and dilute the cartel’s actions without help from Russia and others.

The hard part has been hammering out the details of any such agreement, including how long the production cuts should last, how to enforce the pact and what production statistics should be used as a baseline number. In order to "enforce" compliance, Russia and Oman - the only two nations which have explicitly stated they will cut production instead of waiting "natural" production declines, will join OPEC members Algeria, Kuwait and Venezuela on the committee to oversee implementation of the accord, a delegate said.

Alongside recent oil supply records by many non-OPEC nations, most notably Russia, OPEC production reached an all-time high of nearly 34.2 million barrels a day, well above the group’s target of 32.5 million barrels a day from January.

Libya and Nigeria are exempted from the OPEC output cuts, while Iran has some room to boost its output. All three nations are ramping up their own production aggressively and will make hitting OPEC's reduced production goal that much more unlikely.

As Reuters reported late in the week, Saudi Arabia informed customers in Europe and North America that it would supply less oil in January than December. The United Arab Emirates said on Saturday that it will take similar action. The production cuts, however, come at a time when most OPEC nations announced January selling prices at steep discounts to market as the scramble to capture even market share accelerates and jeopardizes any deal with the incentives to cheat particularly high. Furthermore, the selling price discounts suggest that there has been a far steeper than expected decline in oil demand, mostly out of China and India, suggesting that OPEC's 32.5mmbpd production target could be too high.

Finally, the biggest wildcard in the oil production equation, US shale producers, were completely absent from any negotiation. As reported yesterday, for the 25th of the last 27 weeks, Baker Hughes reported that the US oil rig count rose once again. And with the biggest rise (+21) since April 2014 to 498, the highest since January 2016...

... the jump in oil rigs signals that US shale production is set to rise dramatically in the months ahead, pouring cold water over OPEC and Saudi production cut hopes.