KYIV, Jan 18 (Reuters) - Ukrainian maritime grain exports are expected to fall by around 20% in January from the previous month due to the crisis in the Red Sea and the New Year holidays, a senior Ukrainian government official said on Thursday.

"Looks like it could be around minus 20%. But in any case it would be a very substantial volume," the source told Reuters, declining to be named because of the sensitivity of the matter.

Such a decrease would be a setback for wartime Ukraine which exported a record high amount of food via its Black Sea corridor in December, surpassing the maximum volume exported under a previous U.N.-brokered grain deal in a single month.

Agriculture Minister Mykola Solsky said earlier on Thursday that key Ukrainian food exports might decrease this month because of the situation in the Red Sea.

Attacks by Iran-allied Houthi militia in Yemen on vessels in the region since November have slowed trade between Asia and Europe and alarmed major powers.

The U.S. has begun strikes on Houthi sites aiming to degrade their ability to attack shipping in the Red Sea. (Reporting by Pavel Polityuk; editing by Tom Balmforth and Sharon Singleton)