The United States fears a war within a war as Turkey sent more than 1,000 troops into northern Iraq to bolster its military presence and promised to send more to prevent Iraqi Kurds from creating an independent state.

The mechanised infantry unit, which included armored personnel carriers, crossed into Iraq near the town of Cukurca, where the borders of Turkey, Iraq and Iran converge.

The military is also shifting some 5,000 soldiers to the border region, the official said. Thousands of troops are camped near the town of Silopi, close to the border and about 20 miles south of the town of Cizre.

Turkey delayed opening its airspace to US warplanes, saying that US should first agree to its demands to move troops into northern Iraq. Ankara, later dropped the demand and allowed the overflights.

US Secretary of State Colin Powell on Friday said there was no need for Turkish troops in Northern Iraq, where the Kurds live, but Washington desperately needed overflight rights over Turkey and did not protest too much over the Turkish action.