International Brent crude oil futures slid $1.14 to $66.69 a barrel by 1244 GMT, while US West Texas Intermediate (WTI) crude futures were down $1.02 at $58.39 a barrel.

"Very important that OPEC increase the flow of Oil. World Markets are fragile, price of Oil getting too high. Thank you!" Trump wrote in a post on Twitter.

Brent crude has risen more than 25 percent this year on the back of moves by OPEC and allies like Russia to cut output, as well as plummeting Venezuelan production. On top of US sanctions, power cuts have crippled Venezuela's oil industry.

The country's main oil export port of Jose and four crude upgraders, needed to convert Venezuela's heavy oil into exportable grades, have been halted since Monday, industry sources said.

US sanctions have also hit Iranian crude exports.

Analysts said they expected the United States in early May to extend some sanction waivers on Iranian oil, but might reduce the number of countries receiving them.

The 180-day exemptions were granted in November to China, India, Greece, Italy, Taiwan, Japan, Turkey and South Korea.

"Enjoy it whilst it lasts. The upcoming six months will bring relatively healthy demand for OPEC oil," PVM's Tamas Varga said in a note.

"If the unplanned supply cuts remain in place... oil prices should edge towards $75/bbl ...in coming months as global inventories will draw."

Data from the US Energy Information Administration showing a surprise rise in US crude inventories last week also weighed on prices on Thursday.

Oil stocks rose 2.8 million barrels, the report showed, compared with analysts' expectations for a drop of 1.2 million barrels.

Demand concerns on the back of economic jitters linked to the US-Chinese trade war have further capped prices.

In a fresh development, China made unprecedented proposals on a range of issues, including forced technology transfer, as the two sides work to end their protracted dispute.