FACTBOX: Diplomatic challenges facing Russia's Medvedev

(Reuters) - Diplomatic novice Dmitry Medvedev will take over next week as Russian president with a thick stack of foreign policy challenges in his in-tray.

Here are some of the international issues that will confront Medvedev when he replaces his mentor Vladimir Putin as head of state on May 7:

NATO ENLARGEMENT

The Western military alliance agreed at its summit in Bucharest last month to give ex-Soviet Ukraine and Georgia eventual membership, though it did not set a timetable.

Russia opposes their accession and says it will upset the fragile balance of power in Europe and threaten Russian security by moving NATO hardware and troops up to its southern flank.

MISSILE SHIELD PLAN

Medvedev will also face the quandary of how to stop U.S. plans for a missile defense shield in eastern Europe from going ahead. Washington says the planned radar and interceptor missiles in Poland and the Czech Republic are needed to defend against what it calls "rogue states", specifically Iran.

Moscow suspects the shield will be used to spy on Russia's missile arsenal. Attempts to reach a compromise have made only halting progress.

EU RELATIONS