* Trade thin ahead of Christmas holiday
* U.S.-China trade deal expected to boost energy demand
* U.S. crude inventories low, OPEC+ to cut more supply (Updates with settlement prices)
By Collin Eaton
HOUSTON, Dec 19 (Reuters) - Oil prices reached the highest level in three months in thin pre-Christmas trading on Thursday, buoyed by the previous day's news that U.S. crude inventories declined and as U.S.-China trade tensions continued to ease.
Brent crude futures rose 37 cents to settle at $66.54 a barrel, gaining for the sixth straight day.
U.S. West Texas Intermediate (WTI) crude rose 29 cents to settle at $61.22 a barrel.
Trading volume was thin, with oil headed for a third consecutive weekly rise. Prices were buoyed by China's Dec. 13 decision to cancel a plan to impose additional tariffs on U.S. imports on Dec. 15 and the Phase 1 deal between Washington and China, which has eased trade tensions.
The deal between the world's two largest economies has improved the global economic outlook, lifting prospects for higher energy demand next year and underpinning oil prices.
"The market's happy with (Dec. 15) tariffs out of the way and the trade truce, for now," said Bill Baruch, president at Blue Line Futures in Chicago.
In a further sign of thawing relations, China's finance ministry on Thursday published a new list of six U.S. products that will be exempt from tariffs starting on Dec. 26.
However, if U.S. and Chinese officials fail to provide concrete details about their efforts to reach a trade agreement, oil prices could lose their upward momentum, said Gene McGillian, vice president of market research at Tradition Energy in Stamford, Connecticut.
"Unless we get real granularity, the uncertainty around what's happening on the trade front will start to add more resistance. We need to see signs that a real resolution is at hand," McGillian said.
Another development lifting prices was the agreement this month between the Organization of the Petroleum Exporting Countries and non-OPEC producers such as Russia to deepen production cuts by a further 500,000 barrels per day (bpd) from Jan. 1 on top of previous reductions of 1.2 million bpd.
Adding to the positive mood, weekly data from the Energy Information Administration showed U.S. crude inventories dropped 1.1 million barrels in the week to Dec. 13, while gasoline and distillates stockpiles rose.
News of President Donald Trump's impeachment by the U.S. House of Representatives failed to stir the oil market. (Reporting by Collin Eaton in Houston Additional reporting by Shadia Nasralla in London and Florence Tan in Singapore Editing by David Gregorio and Matthew Lewis)