Approaching 1630 IST, US benchmark West Texas Intermediate (WTI) for delivery in June shed 54 cents to USD 43.19 a barrel.
Brent North Sea crude for June sagged 37 cents to USD 44.74 a barrel compared with Friday's close.
"Prices (are) meandering... As news disperses of a possible Saudi oilfield expansion which could bolster supply, ultimately spelling more problems for a market already excessively oversupplied," said analyst Lukman Otunuga at trading firm FXTM.
Saudi Arabian Oil Co. Will complete an expansion of its Shaybah oilfield by the end of May, allowing the world's largest exporter to maintain total capacity at 12 million barrels a day, Bloomberg News reported.
The move will see Shaybah's capacity rise from 750,000 barrels to 1.0 million barrels a day, the report said.
The report caused "market jitters", said Bernard Aw, an analyst with IG Markets in Singapore.
Prices tumbled initially last Monday after the collapse of a meeting of major producers aimed at freezing output.
However, falling US production, a strike in key producer Kuwait and signs of a pick-up in key market China helped propel an 8.3-per cent surge over the week for WTI, while Brent rose 4.7 per cent.
The oil market had also won support from the Baker Hughes weekly US rig count, which showed oil producers curtailed use of eight drilling rigs in the week ending April 22.
"There's still a little bit of optimism that producers could come to some sort of an agreement in June... The market participants are always quite hopeful of such talks," he noted.
The global oil market had nosedived from above USD 100 in mid-2014 to 13-year lows of around USD 27 in February, plagued by the stubborn supply glut.
Prices have since rebounded on hopes of an output freeze deal, but this failed to materialise at crucial producer talks in Doha earlier this month.
