* Not yet clear if Aramco will keep supply steady to other buyers
* Aramco has raised prices for all crude oil grades to Asia in Jan (Adds detail)
TOKYO, Dec 11 (Reuters) - Saudi Arabia, the world's top oil exporter, will supply full contractual volumes of crude to a North Asian refiner in January, unchanged from the previous month, a source with direct knowledge of the matter said on Monday.
The country supplied full contractual volumes of crude to at least three North Asian refiners for December loading. But it trimmed supplies to at least three Japanese buyers and one in South Korea by up to 10 percent across different Saudi crude grades for November loading as maintenance at oilfields reduced output.
State oil company Saudi Aramco last week raised prices for all crude oil grades to Asia in January.
It was not immediately clear if Aramco would keep supplies steady to other buyers in the region.
At least one North Asian refiner had not received its monthly allocation yet, a source familiar with the matter said, but added that Saudi Arabia was seen as willing to meet buyers' demand.
All sources declined to be identified as they were not authorized to speak with media. (Reporting by Osamu Tsukimori; Editing by Joseph Radford)