Oil futures on Friday were on course for their biggest weekly percentage declines since January of just under 10 percent as signs of tensions resurfaced between Saudi Arabia and Iran that could scupper a key supply cut pact.
Traders also noted a surge in U.S. crude inventories last week and muted demand continued to weigh on futures.
U.S. West Texas Intermediate (WTI) futures were down 59 cents, or 1.3 percent, at $44.07 a barrel, having fallen as low as $43.57 earlier in the session. For the week, it was down more than 9 percent, the biggest decline since mid-January.
Brent crude futures were down 74 cents, or 1.6 percent, at $45.61 per barrel at 2:28 p.m. ET (1838 GMT), off a low of $45.08. It was on pace to end the weed down more than 8 percent.