A survey of 31 economists and analysts polled by Reuters showed Brent crude LCOc1 would average nearly $64 a barrel in 2018, versus $63 forecast in the February survey, but below the $67.18 average for the benchmark so far in 2018.

Brent prices have risen 4 percent this year, supported by a deal between the Organization of the Petroleum Exporting Countries and non-OPEC producers led by Russia to curb output by about 1.8 million barrels per day (bpd) through 2018.

The price briefly rose above $70 a barrel this week, supported by tension in the Middle East and declining output in Venezuela, one of the group’s largest producers, where economic crisis has cut production to its lowest in nearly 30 years.

A sustained drawdown in U.S. inventories also helped push the price up towards $70, a peak last seen in December 2014.

“We view it rather unlikely that OPEC will exit already by mid-year. However, talking about a possible extension of the deal beyond 2018, we are rather skeptical,” Hannes Loacker of Raiffeisen Capital Management said.

“We see a big challenge in bringing in Russia once more. Without Russian participation, the will of some other OPEC members may also be abating somewhat.”

Saudi Arabia and Russia are working on a long-term pact that could extend controls over world crude supplies by major exporters for many years.

“Even if OPEC compliance with pledged supply remains elevated through the balance of 2018, the explosive growth in U.S. shale oil supply accompanied by growth in crude oil export capacity will likely tip the balance towards lower oil prices in the second half,” BNP Paribas analyst Harry Tchilinguirian said.

Analysts expect U.S. production to grow by at least 1 million bpd this year. U.S. output now stands at nearly 10.4 million bpd C-OUT-T-EIA, taking it past top exporter Saudi Arabia and within reach of biggest producer Russia.

A pump jack is seen at sunset near Midland, Texas, U.S., on May 3, 2017. Picture taken May 3, 2017. REUTERS/Ernest Scheyder

“The balance between strong production growth in the U.S., on the one hand, and continued restraint by OPEC and Russia, on the other, remains the key factor on the supply side,” said Cailin Birch, an analyst at the Economist Intelligence Unit.

“On the demand side, emerging Asia will remain the key region for new demand growth.”

The International Energy Agency said this month that global oil demand would increase by 6.9 million bpd by 2023 to 104.7 million bpd, boosted by economic growth in Asia and a resurgent U.S. petrochemicals industry.

Analysts said oil prices could also be pushed up by fears of renewed sanctions on Iranian oil exports after the United States threatened to withdraw from a nuclear deal.

U.S. light crude CLc1 will average $59.85 a barrel in 2018, the poll found, up from $58.88 forecast in February.

Elsewhere, the recent launch of China’s yuan-denominated oil futures, which many expect to become a third global price benchmark alongside Brent and WTI, made a roaring start as Western players and Chinese majors eagerly traded the world’s newest financial oil instrument.