A West German with tough views on defense takes over as Secretary-General of NATO on Friday at a time when some in the alliance say the new warmth in East-West relations is posing almost as big a problem as the cold war.

Manfred Woerner, 53, assumes command with the West cautiously welcoming signs of radical change in the Soviet Union but adamant that the military threat from Moscow remains undiminished.The 16-nation Atlantic alliance faces tough decisions on nuclear and conventional arms control, and Soviet leader Mikhail Gorbachev is forcing the pace.

Woerner, a former defense minister with a hawkish reputation on military issues, succeeds Britain's Lord Carrington, who once described his job as mid-Atlantic - "cold and wet and lonely."

The alliance is short of cash and suffering from transatlantic tensions over U.S. charges that the Europeans are not bearing a fair share of the defense burden.

North Atlantic Treaty Organization officials say Woerner's strong grasp of defense issues will give him a head start.

One of his prime tasks will be to set out arms control priorities for the alliance to avoid a repeat of last year's disarray over the question of scrapping medium-range nuclear missiles.

"Arms control is the big item on his agenda. There's no doubt about that," a NATO diplomat said.

With the U.S. medium-range missiles being phased out in Europe, the next big question is modernizing short-range nuclear systems with a reach under 300 miles.

Bonn has found itself at odds with the United States and Britain by calling for any modernization decision to be postponed for fear of reviving anti-nuclear feeling at home.

Gorbachev has helped set the allies against each other with a proposal on conventional forces in Europe where NATO seeks to wipe out the Warsaw Pact's huge advantage in tanks, artillery and planes.