KIEV (Reuters) - U.S. Vice President Joe Biden will announce a package of technical assistance focused on energy and economic aid distribution during a two-day visit to Kiev, a senior administration official said on Monday.

Briefing reporters onboard Biden's plane, the official said the assistance was made up primarily of technical know-how to help boost energy efficiency as well as production in Ukrainian natural gas fields and extraction of "unconventional" gas resources.

The economic assistance involved U.S. teams to help Ukraine ensure international aid was allocated effectively in all parts of the country, the official said.

Biden will also discuss a recent U.S. tranche of nonlethal security aid for Ukraine and options for following up on that.

"He'll have the opportunity to speak with the government about what more is needed and what more we could provide in the period ahead," the official said.

Biden arrived in Ukraine on Monday and has meetings with government leaders scheduled for Tuesday.

His visit comes as an agreement reached last week to avert wider conflict in Ukraine began to falter. Pro-Moscow separatist gunmen have maintained their grip on seized government buildings across swathes of eastern Ukraine as Washington threatens to impose new economic sanctions on Moscow, which it says it will hold responsible.

Biden's trip to Kiev, the highest-level visit from a U.S. official since the start of the crisis here, was born out of discussions with President Barack Obama, the official said.

"(Biden) wanted to come to Kiev to send a very clear message of the United States' support for Ukraine's democracy, unity, sovereignty and territorial integrity," the official said.

"He will call for urgent implementation of the agreement reached in Geneva last week while also making clear ... that there will be mounting costs for Russia if they choose a destabilizing rather than constructive course in the days ahead."

(Reporting by Jeff Mason; Editing by Sus