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

The European Union is Russia's biggest trading partner but an attempt to draft a new strategic partnership agreement, setting out a road map for deeper relations, has been stalled. Poland vetoed the start of talks on the pact and now ex-Soviet Lithuania is blocking them. Once talks start, they are likely to be beset by disagreements over energy, trade and human rights.

IRAN'S NUCLEAR PROGRAMME

Russia and the West have differences over how to tackle Iran's nuclear program. While the United States seeks tougher sanctions and refuses to rule out military action, Moscow has watered down UN resolutions on sanctions and says armed intervention would have catastrophic consequences.

CHINA

Medvedev faces a difficult balancing act with China. It is a hungry customer for Russian mineral resources. But many in Russia's elite view China's growing economic, political and military clout with suspicion. Officials also worry about large numbers of Chinese crossing the border to work and live in Russia's sparsely-populated Far East region.

GEORGIA

Moscow's relations with its ex-Soviet neighbor Georgia have never been cordial but in the past few weeks they have worsened into a standoff over Georgia's breakaway region of Abkhazia. Some diplomats say hardliners inside Russia are ramping up the tension to push Medvedev into adopting an anti-Western stance.