"We hope that this fight against terrorism will end soon but we don't know how much longer it will last," Erdogan told journalists in Madrid, where he was meeting with Spanish counterpart Jose Luis Rodriguez Zapatero.

"In Afghanistan there are foreign forces fighting against terrorism and they also can't say how long they will have to be there," he added, speaking via a Spanish interpreter.

In October Turkey's parliament voted overwhelmingly to authorise the country's military to send troops into the mountainous terrain of northern Iraq to confront Kurdish rebels in hide-outs there.

The authorisation is valid until October 2008 and Erdogan said if the fighting is not over by then, "we will seek approval for the following year."

Erdogan said Turkey's sole aim was to eliminate the Kurdistan Workers' Party, or PKK rebels, adding every effort was being made to spare civilians.

Some 4,000 "terrorists" were being trained in the region, he estimated.

"Our only objective is to eliminate the terrorists," the prime minister said. "We have the technology and the intelligence to do this without hurting civilians."

Over the past month Turkish military aircraft have regularly carried out bombing runs inside Iraq in an attempt to flush out PKK fighters.

The PKK uses the region to launch attacks against Turkey. It has fought for self-rule in southeastern Turkey since 1984.

Both the United States and the European Union classify the PKK as a terrorist organisation.

Turkey has moved around 100,000 soldiers up to its 380-kilometre (235-mile) border with Iraq.

Erdogan is in Spain to take part in a two-day gathering of world leaders and personalities that gets under way Tuesday in Madrid to launch a United Nations forum aimed at combating fear and suspicion between different cultures.