Crude oil prices were holding near two-year highs on Tuesday, but gains were looking thinner as the rally advanced.
Speculators still believe prices will move higher amid OPEC-led production cuts and a dip in North American drilling activity.
On Tuesday, Nymex West Texas Intermediate, the US benchmark crude contract rose 0.29% to $61.93 a barrel, just shy of its recent peak of $62.55 - the highest level reached since 2015.
Brent crude, currently the global benchmark crude contract, rose 0.19% to $67.91 a barrel, having earlier reached $68.25 - just 2 cents short of its two-year high.
The production cuts by oil cartel OPEC and other countries including Russia are expected to run through this year.
The countries involved hope to bring the forces of supply and demand back into balance to help lift market prices which, for much of 2017 remained in a range between $40-$50 a barrel.
Data showing speculative positioning in the ICE Brent contract showed that 4,175 lots were added to long positions - investing in price rises - leading to a record net long position of 565,459 lots.
But some analysts are concerned that if prices rise much higher, North American drilling will be ramped up to take advantage of the price and ultimately return the market balance to oversupply.
"The bullish momentum seen since June has helped create a record speculative long bet while supporting a strong recovery in US production," said Ole Hansen at Saxo Bank.