Turkey has toughened its rhetoric against Islamic State jihadists but the West is still waiting for action from Ankara after months of frustration with its lukewarm cooperation.
Ankara on Wednesday denied Turkish air space had been used in the latest US-led strikes against IS militants in Syria, but made clear that Turkey strongly supported the campaign.
IS militants have advanced through Kurdish areas in northern Syria, dangerously close to the Turkish border, sparking an exodus of some 140,000 mainly Kurdish refugees to Turkey.
Visiting New York in his first trip to the West since his inauguration as president in August, President Recep Tayyip Erdogan unequivocally denounced IS as a "terrorist organisation".
Moreover, he said that Turkey could offer logistical, intelligence or even military support for the anti-IS campaign, the first time Ankara has suggested offering such assistance.
Turkey, which for the last years has pushed for the overthrow of President Bashar al-Assad, is blamed by some for sparking the rise of IS and then doing precious little to combat it.
For months, the West expressed frustration over Turkey's reticence but Ankara said its hands were tied by the fact dozens of Turkish hostages were held by IS in Iraq.
With the hostages unexpectedly released over the weekend -- reportedly after negotiations with IS in a top secret operation overseen by the Turkish secret service -- Ankara is now adopting a tougher tone on the group.
Erdogan said in New York: "We will take whatever steps necessary to combat terrorism."
- 'Open to all possibilities' -
However Ankara has stopped short of saying what its help could involve and is studiously keeping its options open, even as its allies clamour for immediate assistance.
US Secretary of State John Kerry had said that after the release of the hostages he expected Ankara to be on the "frontlines" of the fight against IS.
Turkey hosts US air forces at its Incirlik air base, an ideal launch base for air strikes in Syria.
"Turkey is evaluating the scope of the support it will give to the operation," Deputy Prime Minister Yalcin Akdogan said on Wednesday.
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"It could be logistic or intelligence cooperation. An operation does not necessarily mean firing bullets."
Ilter Turan, professor of political science at Istanbul's Bilgi University, said it was too early to say that Turkey was dramatically changing its position.
"One should not attribute much significance to words before seeing actions," he told AFP, saying that Turkey was under pressure from its Western allies.
"We can expect a change in Ankara's position but we don't know in what form."
A Turkish official declined to comment on the "technical details" of any such operation against IS insurgency but said military cooperation with allies had different dimensions and taking part as a combat force was only one.
"It would be wrong to reduce (military cooperation) to that," he told AFP.
The official, speaking on condition of anonymity, said a lot of formulations had already been discussed between Turkey and its NATO allies.
"We are open to all possibilities but this does not mean we will take part in operations," the source said.
- New trouble for Kurdish peace -
Turkey is also mindful that the IS assault on Kurdish-populated parts of Syria and the influx of Kurdish refugees has come at a critical moment in its search for peace in the 30-year conflict with Kurdistan Workers' Party (PKK) militants in Turkey.
Its jailed leader Abdullah Ocalan on Tuesday angrily accused the Turkish government of negotiating with IS over the hostages while not re-opening peace talks with the PKK.
Turkey already raised concerns that the weapons sent by Western states may end up at the hands of PKK fighters to launch attacks on Turkish soil.
Amid escalating clashes between Kurdish fighters and IS insurgents, Turkey now places number one priority on establishing a safe zone to help civilians across the border within Syrian soil.
"Turkey has received in three days the same number of refugees accepted by European countries since April 2011," said the official, raising Ankara's concerns about a flood of refugees if IS wages a "do or die" war.
"A safe-zone is very important but requires a no-fly zone and it requires UN approval. This is our priority."