ANKARA - Turkey will oppose a NATO plan to defend Baltic countries unless the alliance backs it in recognising a Kurdish militia as a terrorist group, President Tayyip Erdogan said on Tuesday ahead of an alliance summit in London.
The threat underlined the mounting challenges to a bloc hailed by backers as the most successful military alliance in history just as its leaders, including US President Donald Trump, gather in London to celebrate its 70th anniversary.
Turkey's defiance will only add to doubts over the political future of NATO, already described by French President Emmanuel Macron as "brain dead" and undermined by Trump's questioning of the entire premise of his superpower defending the West.
NATO has mooted a plan to bolster the defences of Poland, Estonia, Lithuania and Latvia against a potential attack from Russia, though details remain unclear. Erdogan, who has strained alliance ties with a move to buy Russian air defence systems, repeated his threat to block the defence plan unless NATO steps up support for its fight in northeastern Syria against the Kurdish YPG militia.
The YPG is closely linked to the Kurdistan Workers' Party (PKK), which has waged a bloody insurgency against Turkey since 1984 and is designated a terrorist organisation by Ankara and its Western allies.
Nonetheless Western countries have used the YPG as a frontline force against the Islamic State group (IS) and opposed Turkey's offensive against them in October.
"With pleasure, we can come together and discuss these issues there as well," Erdogan said of the Baltics plan ahead of his departure from Ankara for the NATO summit.
"But if our friends at NATO do not recognise as terrorist organisations those we consider terrorist organisations... we will stand against any step that will be taken there."
Erdogan added he had spoken to Polish President Andrzej Duda on the phone and had agreed to meet him and leaders of Baltic countries in London. Turkey, France, Germany and Britain are also expected to hold separate meetings around the summit.
There are also tensions over Turkey's recent purchase of the S-400 missile defence system from Russia, which could lead the US to impose economic sanctions.
"Our good relations with Russia and other countries is not an alternative to our relationship with our allies. It's the opposite: it is complementary," Erdogan said.
'Waving or drowning?'
In an interview with Reuters news agency, US Defense Secretary Mark Esper warned Ankara that "not everybody sees the threats that they see", and he urged it, in the name of alliance unity, to stop blocking the Baltics plan.
NATO Secretary-General Jens Stoltenberg reaffirmed the mutual defence clause at the heart of the NATO pact, insisting it would respond to any attack on Poland or Baltic countries.
"Through the presence of NATO forces in Poland and in the Baltic countries, we are sending Russia a very strong signal: if there is an attack on Poland or the Baltic countries, the whole alliance will respond," Stoltenberg, a former Norwegian prime minister, said in interviews with several European newspapers.
Queen Elizabeth will host the leaders at Buckingham Palace. But even the British hosts, for generations among the most enthusiastic champions of the trans-Atlantic partnership that NATO represents, are disunited over their project of quitting the EU and distracted by a rancorous election due next week.
"The question is, as we celebrate 70 years, are we waving in celebration or do people think we are drowning" said a senior European NATO diplomat.
Stoltenberg argues that despite quarrels that have made headlines, the alliance is in fine health, having strengthened its capability to carry out its core mission of defending Europe following Russia's 2014 annexation of Crimea from Ukraine.
"We are faced with a paradox," Stoltenberg said before the summit. "Yes we have some differences, but the reality is that we are doing more together than for many years."
Europe, Turkey and Canada will pledge $400 billion in defence spending by 2024, aiming to placate Trump who has long said US allies need to spend more on the collective defence.
Leaders will also agree a new 2021-2024 budget that reduces the US contribution to fund the alliance itself. They will approve a new strategy to monitor China's growing military activity for the first time, and name space as a domain of warfare, along with air, land, sea and computer networks.
France's Macron sent shivers through the alliance last month when he publicly questioned NATO's central tenet that an attack on one member is an attack against all.
His frustration over a US decision to pull troops from Syria in October, thereby setting the stage for Turkey's unilateral offensive there against the YPG militia, prompted Macron to describe the alliance as "experiencing brain death", as he decried a lack of strategy.
A Franco-German proposal would create a group of eminent figures to consider the alliance's future political role, submitting a report by the next scheduled summit in late 2021.
Wariness of Russia may prove to be a unifying factor, diplomats said. Leaders will issue a statement condemning Moscow's Crimea annexation and its military build-up, recommitting to the alliance's collective defence pledge.