By Paul Tait

BAGHDAD, Jan 29 (Reuters) - It is too soon to describe operations against al Qaeda in northern Iraq's Mosul as a final push because its Sunni Islamist gunmen could regroup elsewhere, the commander of U.S. forces in the area said on Tuesday.

Iraqi Prime Minister Nuri al-Maliki last week announced what he described as a "decisive" final push against al Qaeda in Mosul, Iraq's third-largest city, which U.S. commanders call the group's last major urban stronghold.

But Major-General Mark Hertling said the fight against al Qaeda in the north and elsewhere in Iraq was part of continuing offensives against the group, which is blamed for most large-scale attacks in Iraq.

"The moment we say this offensive is the final push, they're going to creep off somewhere else and regroup," Hertling told Reuters by telephone.

"I'm just not confident enough to say this is the final push against AQI (al Qaeda in Iraq) in Mosul," he said, adding he did "not want to get crossways" with Maliki's government.

"What we can say is that there has been an attempt by AQI to gain control of Mosul. We have to not allow them to get that stronghold," he said. The U.S. military regards al Qaeda as the biggest single threat to security in Iraq.

Extra Iraqi troops, backed by helicopters and tanks, began arriving in Mosul late on Sunday.

Maliki's government has given no firm information about how many additional troops will be deployed in Mosul as part of the push but has said it will include 3,000 more police.

Hertling said he was aware of the government's plan and was working closely with his Iraqi counterparts but would give no further details.

BLAST

Maliki announced the push against al Qaeda in Mosul after a massive blast in the city last week. Officials put the death toll at 40, with 240 wounded, but the Iraqi Red Crescent said 50 died.

The U.S. military said the explosion was in a building used by al Qaeda to store weapons and tonnes of explosives. A senior police officer was killed by a suicide bomber dressed in a police uniform as he inspected the site the next day.

On Monday, five U.S. soldiers were killed by a roadside bomb and their patrol came under small arms fire in a coordinated ambush in eastern Mosul.

Hertling said fighting lasted for about two hours after the ambush but said some of the gunmen were later captured.

Al Qaeda has regrouped in Mosul and other parts of northern Iraq after being squeezed out of former strongholds in western Anbar province and from around Baghdad during security crackdowns last year.

Violence has fallen sharply across Iraq. Washington says attacks are down 60 percent since last June but the northern provinces of Nineveh, of which Mosul is the capital, Salahuddin, Kirkuk and Diyala remain the biggest worries.

The U.S. military has begun a series of offensives in those provinces, part of a wider operation targeting the north and areas south of Baghdad which began early this month.

Hertling said significant gains had been made in Diyala and Kirkuk, with the growth of U.S.-backed neighbourhood police units organised by mainly Sunni Arab tribal sheikhs playing a part in securing former troublespots. (Editing by Andrew Roche)

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