TOKYO: Oil prices rose on Monday, adding to gains in the first quarter when the major benchmarks posted their biggest increases in nearly a decade, as concerns about supplies outweigh fears of a slowing global economy.

Brent crude for June delivery was up by 43 cents, or 0.6 per cent, at US$68.01 a barrel by 0214 GMT, having risen 27 per cent in the first quarter, report agencies.

US sanctions on Iran and Venezuela along with supply cuts by members of the Organization of the Petroleum Exporting Countries (Opec) and other major producers have helped support prices this year, overshadowing concerns about global growth and the US-China trade war.

However, future gains will be limited by potential softness in the global economy as well as the ability of US oil producers to ramp up production when prices spike, said Phin Ziebell, senior economist at National Australia Bank in Sydney.

"It's tough to see a really big rally from here," he said.

Still, analysts have turned cautiously optimistic on crude oil prices this year, a Reuters poll showed on Friday.

US production has also steadied, with the US government reporting on Friday that domestic output in the world's top crude producer edged lower in January to 11.9 million bpd.

Sigal Mandelker, US under-secretary of the Treasury for Terrorism and Financial Intelligence, told reporters in Singapore on Friday that the United States had placed further "intense pressure" on Iran.

US officials are keen to ensure see that Malaysia, Singapore and others are fully aware of illicit Iranian oil shipments and the tactics Iran uses to evade sanctions, Ms Mandelker said.