* U.S. moves closer to oil self-sufficiency
* Non-OPEC to meet most oil demand growth to 2020
* OPEC struggling to increase output
* IEA sees healthy global oil demand growth to 2023 (Adds details, data, quotes)
LONDON, March 5 (Reuters) - U.S. shale oil output is set to surge over the next five years stealing market share from OPEC producers and moving the country, once the world's top oil importer, closer to self sufficiency, the International Energy Agency said on Monday.
A landmark deal in 2017 between OPEC and other oil producers including Russia to curb output to reduce global oversupply materially improved the outlook for other producers as oil prices rose sharply throughout the year, the IEA said.
As a result, U.S. oil output has resumed sharp growth over the past year and is expected to rise by 2.7 million barrels per day (bpd) to 12.1 million bpd by 2023, as growth from shale fields more than offsets declines in conventional supply.
Natural gas liquids will add another 1 million bpd to reach 4.7 million bpd by 2023.
With total U.S. liquids production set to reach nearly 17 million bpd in 2023, up from 13.2 million in 2017, the United States will be by far the world's top oil liquids producer.
"The United States is set to put its stamp on global oil markets for the next five years," Fatih Birol, the IEAs executive director, said in a medium-term market outlook.
Oil production growth from the United States, Brazil, Canada and Norway will more than meet global oil demand growth through 2020, the IEA said, adding that more investment would be needed to boost output after that.
Non-OPEC production is set to rise by 5.2 million bpd by 2023 to 63.3 million bpd with the United States alone accounting for nearly 60 percent of global supply growth.
Growth will be led by the Permian Basin in Texas and New Mexico, where output is expected to double by 2023.
"Despite talk of capital discipline and increased focus on returns rather than growth, U.S. producers regrouped quickly when oil prices stabilised and began to rise," the IEA said.
Production in 2017 rose by 670,000 bpd as drillers added 200 rigs "beating all expectations", the IEA said.
Last year, the IEA forecast U.S. shale production to grow by 1.4 million bpd by 2022 with oil prices of up to $60 a barrel and by up to 3 million barrels with oil at $80 a barrel.
By contrast, output from OPEC producers will grow at a much slower pace, the IEA said, adding it expected Venezuelan production declines to accelerate offsetting gains in Iraq.
As a result, OPEC's crude oil capacity will grow by just 750,000 bpd by 2023.
With forecast capacity of 36.31 million bpd, OPEC will be supplying less than 35 percent of global demand by 2023 compared to its usual share of around 40 percent.
Boosted by economic growth in Asia and a resurgent U.S. petrochemicals industry, global oil demand will increase by 6.9 million bpd by 2023 to 104.7 million, according to the IEA.
That means demand growth of around 1.1 percent per year on average.
Despite steep non-OPEC oil production gains, the IEA warned that a decline in mature fields meant more investment was needed across the globe after 2020.
"Upstream investment shows little sign of recovering from its plunge in 2015-2016, which raises concerns about whether adequate supply will be available to offset natural field declines and meet robust demand growth after 2020," it said. (Reporting by Ron Bousso and Dmitry Zhdannikov; editing by Jason Neely)