Pumpjacks are seen against the setting sun at the Daqing oil field in Heilongjiang
Pumpjacks are seen against the setting sun at the Daqing oil field in Heilongjiang province, China December 7, 2018. Reuters

Oil prices were roughly unchanged on Monday as investors weighed the prospect of tighter supplies from OPEC+ producers from May against concerns about weakening global growth that may dampen fuel demand.

Brent crude futures slipped 5 cents to $85.07 a barrel by 0237 GMT, while U.S. West Texas Intermediate crude was at $80.72 a barrel, up 2 cents.

Both contracts rose for a third straight week last week, returning to levels last seen in November, after the Organization of the Petroleum Exporting Countries and their allies surprised investors by announcing more production cuts that will start in May.

The group known as OPEC+ will be cutting mostly sour crude supplies from Middle East producers led by Saudi Arabia.

Following the announcement, the world's top oil exporter raised its May crude prices to term customers in Asia and the United States. State oil giant Saudi Aramco has also notified several Asian customers that they will receive full contract volumes in May despite the production cut.

"Those who were bearish are questioning the demand outlook in light of the cuts, whilst clearly those who were bullish are now seeing even a tighter market over the second half," ING's head of commodities research Warren Patterson said.

"I am in the latter camp and still see prices moving higher from here as we go through the year."

Separately, investors are watching the progress of talks between Iraq and Kurdistan to restart northern oil exports which could bring more sour crude to the global market.

Further supporting prices, the number of U.S. oil rigs fell by two to 590 last week, while gas rigs dropped by two to 158, according to a Baker Hughes Co report on Thursday, a sign that U.S. production won't be rising in the near term.

In global financial markets, the closely watched U.S. inflation report to be released this week could help investors gauge the near-term trajectory for interest rates.

Despite expectations that the Federal Reserve could slow down rate hikes because of the recent banking crisis, borrowing costs could still climb if inflation remains strong, analysts said.

ING expects the rate hike cycle to end soon with one more increase in May while interest rates could fall towards the end of the year, Patterson said.

"The market is probably more worried about the growing possibility of a hard landing," he added.

Sharp rate hikes have boosted the greenback, making dollar-denominated commodities such as oil more expensive for investors holding other currencies.