All 28 Nato members are joining an extraordinary meeting to discuss Turkey’s campaign against the Islamic State (IS) group and Kurdish militants.
The meeting was called by Turkey, which has staged a dramatic shift in its approach to the Syrian conflict.
The previously reluctant partner in the US-led coalition against IS has launched raids against IS in Syria.
Turkey’s prime minister said he expects his country’s allies to show solidarity and support for its campaign.
Analysts say a factor in its change in stance on the Syrian conflict are plans – not yet formally announced – to establish an “Islamic State-free zone” along its Syrian border in collaboration with the US.
As well as targeting IS militants, it would also allow Turkey to hit positions held by the Kurdish PKK group. Turkey says it draws no distinction between the PKK and IS, considering them both as terrorist organisations.
In a series of cross-border strikes since Friday, Turkey has not only targeted IS but also Kurdish fighters affiliated with forces battling the extremists in Syria and Iraq.
Meanwhile Turkish police have continued to arrest suspected members of IS, the PKK and leftist groups – more than 1,000 over the past week.
Under the plans being finalised for the buffer zone, the militants would be removed from a 68-mile (109km) stretch west of the Euphrates River, officials say.
Such a deal would significantly increase the scope of the US-led air war against IS in northern Syria.
Last week Turkey agreed to allow the US to use its air base in Incirlik to launch air strikes against IS.
The Turkish government has long denied turning a blind eye to the rise of IS – or even actively backing the jihadists against the Assad regime, says the BBC’s Mark Lowen in Istanbul.
But a wave of militant strikes has prompted it to take action.
Nonetheless, critics believe Turkey is only striking the jihadists as cover for going after its real enemy: the Kurds, our correspondent says.
The Turkish government’s reluctance to hit IS earlier, the argument goes, was actually a reluctance to help Kurds fighting IS militants.
Now both can be bombed, Turkey is willing to get involved, he adds.
Analysis: Paul Adams, BBC diplomatic correspondent
Turkey’s long-awaited involvement in the international coalition against IS, flying combat missions and making its vital airbases available to US jets, has been described as a possible “game changer.”
But if the government in Ankara continues to see no difference between IS and the Kurdish PKK – a position repeated on Monday by Foreign Minister Mevlut Cavusoglu – then its latest move presents the rest of the coalition, in particular the Americans, with a dilemma.
For almost a year, Kurdish rebels (the YPG, closely allied with the PKK) have represented Washington’s best hope for confronting IS on the ground in Syria.
But Turkey has no interest in promoting Kurdish success along its southern border, at a time when its own unresolved Kurdish conflict threatens to explode once more.
Turkish press fears new civil war
Turkey, a key Nato member, called Tuesday’s meeting of the North Atlantic Council under Article 4 of the alliance’s founding treaty.
The clause allows members to request a summit if their territorial integrity or security is threatened.
It is only the fifth time in the alliance’s history that a member state has requested such a meeting.
The strikes followed a wave of attacks by militants on Turkish soil.
“The Turkey-Syria border, the Turkey-Iraq border is Nato’s responsibility to protect,” Prime Minister Ahmet Davutoglu said.
“Rather than an operational decision [at Tuesday’s meeting], we are hoping all allies understand Turkey’s intentions and for them to support Turkey in its security measures when needed in the ongoing fight.”
Turkey is struggling with more than 1.8 million refugees from the Syrian conflict. On 20 July IS-linked militants killed 32 people in the Kurdish-majority town of Suruc, near the Syrian border.
The crisis has exacerbated tensions in a part of Turkey where a conflict between the outlawed Kurdistan Workers’ Party (PKK) and government troops has killed about 40,000 people since 1984.
The PKK claimed an attack which killed two Turkish police officers on Thursday. It said it was in retaliation for the Suruc bombing and what the group sees as Turkey’s collaboration with IS.
Turkish operations in Syria have also led to tensions with Kurdish militia forces fighting IS in northern Syria.
On Monday Kurdish People’s Protection Units (YPG) said Turkish tanks had shelled their positions near the Syrian town of Kobane.
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