The sources said Saudi Energy Minister Khalid al-Falih and his Russian counterpart Alexander Novak agreed during a series of meetings to lift output from September through December as crude headed towards $80 a barrel. It is now over $85.
"The Russians and the Saudis agreed to add barrels to the market quietly with a view not to look like they are acting on Trump's order to pump more," one source said.
"The Saudi minister told (U.S. Energy Secretary Rick) Perry that Saudi Arabia will raise output if its customers asked for more oil," another source said.
Originally, the two countries had hoped to announce an overall increase of 500,000 barrels per day (bpd) from Saudi-led OPEC and non-OPEC Russia at a gathering of oil ministers in Algiers at the end of September.
But with opposition from some in OPEC, including Iran which is subject to U.S. sanctions, they decided to defer any formal decision until a full OPEC meeting in December.
PERRY LOOPED IN
Since then, Reuters has reported that Riyadh planned to lift output by some 200,000 bpd to 300,000 bpd from September to help fill the gap left by lower Iranian output due to the sanctions.
Russian output rose 150,000 bpd in September.
"I would expect Russia's oil production will hover at around 11.4 to 11.6 million bpd until the end of 2018 and may increase further to 11.8 million bpd later on in 2019," a source at a major Russian oil company said.
Russian produced 11.36 million bpd in September, up from 11.21 million bpd in August, Energy Ministry data showed.
Perry was made aware of the Saudi-Russia plan to lift output before the Algiers gathering, meeting with Falih three times in September and Novak once. The three did not meet together.
Perry's spokeswoman Shaylyn Hynes did not comment on details of the talks but said the energy secretary, "continues to be engaged with leaders from other major oil producing nations and remains confident in their ability to boost output if needed".
She said Perry had in recent meetings "impressed upon his counterparts that keeping supply up is important for the global economy".
Oil prices rose to $85 a barrel this week as buyers of Iranian crude wound down their purchases to meet the terms of U.S. sanctions on Tehran.
Sources said Riyadh would help fill that shortfall because buyers needed replacement supplies. Saudi Arabia has spare capacity to produce oil at a higher rate and holds a large volume of crude in storage.
At the same time, Saudi Arabia is keen to maintain unity among the so-called OPEC+ alliance, a group comprising OPEC states, Russia and several other producers that has agreed on output curbs. That's because it may need to change course and seek the collaboration of OPEC+ for any future production cuts.
In the run up to the private deal with Russia, Falih flew to the United States during the second week of September where he and fellow Texas A&M University alumnus Perry attended a football game in College Station, Texas.
Falih then held official talks with Perry in Washington on Sept. 10, the U.S. Energy Department has said.
Perry flew to Moscow two days later to meet Novak, while Falih also met Novak in Moscow a day later.
Perry told Reuters during his Moscow visit that Saudi Arabia, the United States and Russia had enough capacity between them to compensate for the loss of Iranian supply over the next 18 months.
After Moscow, Falih and Perry met again in Vienna where they attended an event in the Austrian capital, sources said.
"Perry was aware that Russia is going to ramp up oil output," a third source familiar with talks said.
It was at this point that Falih and Novak discussed announcing a 500,000-bpd increase at the Sept. 23 Algiers meeting of OPEC and non-OPEC countries. The plan did not materialise, with any formal decision deferred until a regular OPEC meeting in Vienna on Dec. 6.
"Saudi Arabia is not going to flood the market and risk a price crash. Saudi Arabia has to work with other producers and see what are they doing, who is raising exports and to which market," another source said.
(Additional reporting by Timothy Gardner in Washington; editing by Richard Mably and David Clarke) ((email@example.com; +971 562 160 434; Reuters Messaging: firstname.lastname@example.org ; Twitter: https://twitter.com/Rania_ElGamal))