By Henning Gloystein
Brent crude oil futures were at $73.89 per barrel at 0056 GMT, down 17 cents, or 0.2 percent, from their last close.
U.S. West Texas Intermediate (WTI) crude futures were down 21 cents, or 0.3 percent, at $68.19 a barrel.
U.S. drillers added five oil rigs drilling for new production in the week ending April 20, bringing the total count to 820, the highest since March, 2015, according to General Electric's Baker Hughes energy services firm.
The rising rig count points to further increases in U.S. crude production, which has already climbed by a quarter since mid-2016 to a record 10.54 million barrels per day (bpd).
Only Russia currently produces more, at almost 11 million bpd.
Despite the dips in crude oil prices on Monday, overall markets remain well supported by strong demand, especially in Asia, and Brent prices are up by 20 percent from their 2018 lows in February.
Providing further support have been supply cuts led by the Organization of the Petroleum Exporting Countries (OPEC) introduced in 2017 with the aim of propping up prices.
"Added price pressure comes from U.S. sanctions against the key oil exporting nations of Venezuela, Russia and Iran," said J.P. Morgan Asset Management Global Market Strategist Kerry Craig, referring to action the U.S. government has already taken on Russian companies and individuals, as well as on potential new measures against struggling Venezuela and especially OPEC-member Iran.
The United States has until May 12 to decide whether it will leave the Iran nuclear deal and instead impose new sanctions against Tehran, including potentially on its oil exports, which would further tighten global supplies.
"Stay long oil," U.S. bank J.P. Morgan said in a separate note to clients.
Meanwhile, the generally elevated oil prices have sparked a spat between U.S. President Donald Trump and producer cartel OPEC.
Trump last Friday accused OPEC of "artificially" boosting oil prices, threatening on Twitter that this "will not be accepted", drawing rebukes from several of the world's top oil exporters within OPEC.
(Reporting by Henning Gloystein; Editing by Joseph Radford)
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)