By Jane Arraf CNN Ankara Bureau
ANKARA, Turkey (CNN) -- Turkish military sources said Thursday the United States has beefed up its presence at Incirlik Air Base in south-central Turkey.
The American base is used to monitor and bomb northern Iraq on a regular basis as part of Operation Northern Watch -- the operation that maintains the northern no-fly zone established after the Gulf War.
Turkish military sources said the base seems to be gearing up for a major strike on Iraq -- more than just the routine patrolling of the northern no-fly zone.
In the two days since the terrorist attacks in Washington and New York, the United States has sent in more troops to bulk up its force of 7,000 troops already there, the sources said.
Movement in the towns surrounding the air base also has been restricted, they said.
The Pentagon had no immediate comment.
Turkish Prime Minister Bulent Ecevit told CNN Thursday in Ankara that Turkey would allow the base to be used on any attack against neighboring Iraq, as part of its commitments to NATO.
On Wednesday, NATO invoked a Cold War-era mutual defense clause indicating the alliance's support of the United States. It was the first time in NATO's 52-year history the clause was invoked.
"It is a very powerful signal to the international community and to those who dabble in terrorism or who harbor terrorists, that the Western alliance will not stand easily by," said NATO Secretary-General George Robertson.
According to Article 5, the cornerstone of the alliance, "an armed attack" against any of the NATO members "shall be considered an attack against them all."