U.S. crude for October delivery rose 72 cents to $68.74 a barrel by 1246 GMT (8:46 a.m. EDT). Brent crude was up $1.03 at $67.85 a barrel, having hit an intra-day high of 68.05.
Group of 20 finance leaders, who met in London on Saturday, said they would not end economic stimulus plans until the recovery was well entrenched.
Traders predicted the G20's extended financial support would translate into higher fuel demand.
Along with U.S. data released late last week showing a slowdown in worker layoffs, the G20's decision helped lift Asian and European shares. Positive equities in turn helped push the dollar down against both sterling and the euro.
But analysts said price gains were likely to be limited because many U.S. investors would be absent for Labor Day, which marks the end of the summer holiday season during which gasoline demand rises.
Markets are always looking for direction, currently especially from equity markets. We don't have fundamental driving forces (today) in the oil market, therefore moves are very, very minor in amplitude, said Andy Sommer, analyst with EGL in Switzerland.
I wouldn't expect much to happen during the day because American players are not in today.
Oil prices, which fell 6.5 percent last week, have been trading in a range between $65 and $75 a barrel since the start of August, with prices swinging on economic data as investors seek clues about the speed of a recovery from the recession.
Oil came under pressure last week on concerns over the jobless rate in the United States, which hit a 26-year high, although the pace of layoffs slowed.
Increased crude supplies from the Organization of the Petroleum Exporting Countries (OPEC) due to slipping compliance, could also put downward pressure on oil prices in the near term, analysts said.
OPEC ministers meeting in Vienna this week were expected to keep supply targets intact and instead rely on hoped-for economic growth to sustain oil prices.
Delegates already in Vienna ahead of the meeting, which begins late on Wednesday, told Reuters they were satisfied with the oil price, even though inventory levels were much higher than OPEC considers appropriate.
The market is also watching a weather disturbance that is moving westward from Africa. There is a medium chance of it becoming a tropical cyclone in the next 48 hours, the U.S. National Hurricane Center said on Sunday.
Crude oil speculators on the New York Mercantile Exchange reduced their net long positions in the week to Sept 1, the Commodity Futures Trading Commission said in a report on Friday.
(Additional reporting by Fayen Wong in Perth; editing by Keiron Henderson)