UPDATE 4-Trump rails against high oil prices, OPEC pushes back

* OPEC's Barkindo: output cuts helped rescue oil industry

* Trump's first OPEC tweet on social media as president

* Concern about renewed Iran sanctions driving bullish bets (Updates with additional detail on global inventories, strategic reserve, changes quotes, notes this is Trump's first OPEC tweet as president, updates bullets)

WASHINGTON/DUBAI, April 20 (Reuters) - U.S. President Donald Trump accused OPEC on Friday of "artificially" boosting oil prices after a year-plus pact that has slashed global crude inventories, drawing rebukes from oil-producing countries as prices dipped following his remarks.

"Looks like OPEC is at it again. With record amounts of Oil all over the place, including the fully loaded ships at sea. Oil prices are artificially Very High! No good and will not be accepted!" Trump wrote on Twitter.

It was unclear what triggered the tweet, Trump's first mention of OPEC on social media during his term. It came shortly after Saudi Arabian officials said they remained far from their goal in reducing a three-year global supply glut. Earlier this week, three officials from the country, the world's leading oil exporter, told Reuters they would be happy to see oil hit $80 or $100 a barrel.

This week, oil prices rose to levels not seen since late 2014, and the cartel is expected to restrain supply through the end of this year. While the supply pact has boosted prices, analysts noted that Trump's aggressive stances on Iran and Venezuela have also contributed to oil's gains.

Several members of the Organization of the Petroleum Exporting Countries responded to the tweet, saying prices were not artificially inflated.

OPEC Secretary General Mohammed Barkindo said the output cut agreement halted the collapse in global oil prices, and is "on course to restore stability on a sustainable basis in the interest of producers, consumers and the global economy."

The group is slated to meet in June to decide next steps after reducing output since January 2017 along with other producers including Russia.

"We have a difficult time seeing how OPEC would in any way be swayed here in terms of changing course, in terms of policy," said Michael Tran, commodity strategist at RBC.

Trump gave no details on what action his administration might take regarding oil or OPEC, and the White House did not immediately respond to a request for comment.

OPEC's landmark agreement with other producers cut production beginning in 2017. Since then, oil prices have surged to 3-1/2 year highs, with U.S. crude recently nearing $70 a barrel. The deal could potentially extend into 2019.

OPEC's output fell in March to an 11-month low, according to a Reuters survey. The cartel has targeted the five-year average of inventories in 35 Organization for Economic Cooperation and Development (OECD) countries as a barometer for the deal's success. As of mid-April, those inventories were 2.85 billion barrels, or 43 million more than the five-year average; a year ago, it was 268 million barrels above that benchmark.

This week, crude futures benchmarks Brent and U.S. West Texas Intermediate (WTI) hit their highest since November 2014, with Brent touching $74.75 and U.S. crude $69.56 per barrel.

That has raised fuel costs, with average U.S. prices for gasoline hitting $2.75 a gallon on Wednesday, according to motorist advocacy group AAA, up more than 30 cents from a year earlier.

Trump is just trying to relate to his base when it comes to the retail gasoline prices, so hes blaming OPEC for this," said Josh Graves, senior market strategist at RJO Futures in Chicago.

Brent crude futures were at $73.43 per barrel at 11:33 a.m. EST (1524 GMT), down 38 cents from their last close. WTI futures were down 29 cents at $68 a barrel.

Beyond OPEC's supply management, crude prices have been supported by expectations that Washington will re-introduce sanctions on OPEC-member Iran, and might expand sanctions against Venezuela after that country's presidential elections next month.

"One of the major variables thats fueling the rally in oil prices is the markets perception that (Trump's) administration is taking an increasingly hawkish stance on foreign policy," Tran said.

Hedge funds and other speculators currently hold a record level of bullish bets in Brent, on expectations of further price rises.

The U.S. government cannot legally influence oil prices other than through releasing oil from its strategic reserves which it does occasionally.

This year's budget agreement includes the sale of about 100 million barrels of crude oil - about 15 percent of the reserve - as U.S. oil production recently hit a record at more than 10 million barrels a day. Analysts said it signaled Washington was less concerned about global shortages.

"Washington has fully given up this idea of scarcity. You dont get to the point of selling your strategic reserves to balance your budget if you think the world is short," said Kevin Book, managing director at Clearview Energy Partners. (Reporting by Susan Heavey in Washington, Rania El Gamal in Dubai, Alex Lawler in London, Stephanie Kelly, Ayenat Mersie and Scott DiSavino in New York; Editing by Chizu Nomiyama, Jeffrey Benkoe, Frances Kerry and David Gregorio)