US West Texas Intermediate (WTI) crude oil futures pushed through $56 per barrel for the first time this year, hitting $56.13 a barrel before edging back to $56.02 a barrel by 0112 GMT, still up 0.8 per cent from their last settlement.
For both benchmarks, these were their highest levels since November 20, 2018.
The Organization of the Petroleum Exporting Countries (Opec), as well as some non-affiliated producers like Russia, agreed late last year to cut output by 1.2 million barrels per day (bpd) to prevent a large supply overhang from swelling more.
Traders said financial markets, including crude futures, were also generally supported by hopes that the United States and China would soon resolve their trade disputes, which have dragged on global economic growth.
"Positive signs in the US-China trade talks helped boost sentiment across markets," ANZ bank said on Monday.
At least partly offsetting supply falls has been a surge in US crude oil production by more than 2 million bpd in 2018, to a record 11.9 million bpd.
And there are signs that US output will rise further.
US energy firms last week increased the number of oil rigs looking for new production by three, to a total of 857, energy services firm Baker Hughes said in a weekly report last Friday. RIG-OL-USA-
That means the US rig count is higher than a year ago when fewer than 800 rigs were active.