By Aija Krutaine

RIGA, Feb 14 (Reuters) - Assuming a ceasefire between Ukrainian forces and pro-Russian rebels in the east holds, the implementation of a special constitutional status for the region is likely to be very difficult, according to Latvia's foreign minister.

The deal agreed by Russia and Ukraine in Minsk on Thursday calls for fighting to cease from Sunday; the withdrawal of heavy weapons from the front line; and constitutional reform to give eastern Ukraine more autonomy.

Edgars Rinkevics, whose country holds the rotating presidency of the European Union, said the special status of the separatist Donetsk and Luhansk regions could present particular problems, as could the extent of constitutional reform.

"We see that a serious issue will be the constitutional reform of Ukraine with some decentralisation elements," Rinkevics told Reuters late on Friday. "The special, regional status of the Russian language might be one of issues."

"Indisputably, the practical implementation will be very problematic," added Rinkevics. "It is a success of diplomacy. But now starts the biggest difficulty - finally these agreements have to be implemented, so to say, on the ground."

Fighting intensified in eastern Ukraine on Saturday ahead of the ceasefire, with separatists pressing government forces in the strategic town of Debaltseve, and shelling killing at least one person in the rebel-held city of Donetsk.

The United States and Europe have threatened further sanctions against Moscow if the rebels seize more territory. Rinkevics said a package of steps were being considered by the European Union.

"I would like to stress that sanctions is not our aim. Our aim is that this agreement would be implemented," said Rinkevics. Latvia, which only gained independence from Moscow in 1991, has been among the sanctions hawks.

"Of course, if the situation improves, we set aside this package. If situation worsens, we will review this package."

(Writing by Alistair Scrutton; Editing by)

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