The main principle of NATO is to pay regard to security challenges and threats faced by its members, President Recep Tayyip Erdoğan said Thursday, emphasizing the necessity for Ankara to receive the necessary support against terrorist organizations as the only country in the alliance fighting against several terrorist groups at once.

Speaking to journalists accompanying him during his visit to London for the NATO summit on Dec. 3-4, Erdoğan said the main topics throughout the summit were the refugee crisis, burden-sharing, cyber and hybrid threats, empowering solidarity within the alliance and relations with Russia and China, adding that he also shared Turkey’s security concerns with other members.

"The allies should pay regard to Turkey’s concerns just as we took the security challenges of the alliance seriously. We expressed during the summit and in bilateral meetings that there cannot be an alliance without solidarity," the president said.

"It was unfortunate to see that some allies continue their cooperation with terrorist organizations while emphasizing the struggle against terrorism at the same time," he added.

A member of the bloc since 1952, Turkey boasts NATO's second-largest army after the U.S. It is also currently one of the countries that contributes the most to NATO missions and operations using advanced technology on land, at sea and in the air.

Underscoring Turkey’s responsibility in various task forces from Iraq to Afghanistan, Erdoğan said Ankara has made significant military and economic contribution to the alliance since the beginning of its membership in 1952, also noting that defense spending has reached 1.9% of its total GDP.

Defense spending has been a strain in alliance relations since U.S. President Donald Trump began frequently criticizing alliance members, notably Germany, complaining that many have not met their goal of devoting 2% of economic output to defense spending.

Next quartet meeting to be held in Istanbul

Touching on the quartet meeting between Turkey, France, Germany and the U.K on Syria, Erdoğan said that in the upcoming period, these meetings will be organized at least once a year and that the next gathering will take place in Istanbul in February. He added that the Turkish side presented the information and documents on Ankara’s efforts in the Operation Peace Spring area to its interlocutors.

On Tuesday, Erdoğan convened with French President Emmanuel Macron, German Chancellor Angela Merkel and British Prime Minister Boris Johnson ahead of the formal talks of the NATO summit. During the hourlong meeting, the quartet discussed the Syrian crisis while touching upon Turkey's military operation against terrorist PKK elements in northern Syria, namely the group's Syrian wing, the People’s Protection Units (YPG).

"They are dwelling on our existence in Syria. We share a 911-kilometer border with Syria. So we are asking them, ‘What are you doing here? How dare you ask this question to us?’" Erdoğan said.

He added that Turkey is responsible of establishing a 120-km-long and 32-km-deep safe zone in northern Syria to facilitate the return of Syrian refugees, calling on other members to take a role in the logistics of this project.

On Oct. 9, Turkey launched Operation Peace Spring to clear YPG terrorists from the area east of the Euphrates in northern Syria to secure Turkey's borders, aid in the safe return of Syrian refugees and ensure Syria's territorial integrity.

As agreed in two separate deals with both the U.S. and Russia, Turkey has temporarily halted the operation to allow for the withdrawal of YPG terrorists from the proposed safe zone inside Syria.

Ankara wants YPG terrorists to withdraw from the region so a safe zone can be created to pave the way for the safe return of some 2 million refugees from Turkey.

'Very productive' discussions on S-400, F-35 with Trump

Erdoğan said that he held a "very productive" meeting with Trump, in which the establishment of working groups on the $100 billion trade volume target, the S-400 defense systems and the acquisition of F-35 fighter jets was discussed.

"We also discussed regional issues," Erdoğan said.

After protracted unsuccessful efforts to purchase Patriot missiles from the U.S., Turkey signed a deal with Moscow in April 2017 to acquire the Russian S-400 air defense system, which was delivered earlier this year. Following the acquisition, Turkey was dismissed from the F-35 program and the training of Turkish pilots was suspended, although the country has fulfilled all the necessary financial commitments to the program. After the decision, Erdoğan said that Turkey would turn elsewhere for fighter jets if the U.S. would not sell it the F-35 jets.

Noting that bilateral meetings with the Spanish and Greek prime ministers were also held on the sidelines of the summit, Erdoğan said that he communicated Ankara’s expectation of more awareness from Athens on the deportation of fugitive members of the PKK, Revolutionary People's Liberation Party-Front (DHKP-C) and Gülenist Terror Group (FETÖ) in his meeting with Greek Prime Minister Kyriakos Mitsotakis.

For decades, Greece has served as a safe haven for the DHKP-C and other terrorist groups active in Turkey, granting political asylum to its members.

Greece has long been one of the countries in which the DHKP-C is very active, and the terror group currently operates a camp disguised as a refugee camp, located in the town of Lavrion, 60 kilometers (37 miles) southeast of Athens. Athens' rejection of Turkey's extradition request for eight soldiers involved in the 2016 coup bid engineered by FETÖ has also received harsh criticism from Ankara.

Libya agreement submitted to Parliament

The Libya agreement signed with the official government was submitted to Parliament and the process is going on, after which the agreement will come into force, the president explained.

"But the other side is disturbed. Naturally, those who claim rights to things, for which they have none, are disturbed by such a situation. Particularly Greece, Egypt, the Greek Cypriot Administration of southern Cyprus and Israel are troubled, while they also provoke Europe," Erdoğan said, adding that France and Germany also touched upon the issue during Tuesday’s quartet meeting in London.

Explaining that France did not change its stance even after the necessary explanations were made, Erdoğan said "I told him (Macron), ‘Why are you insisting on this issue? Do you have any rights here? Turkey, Greece and the U.K. are the guarantors here. We use our guarantor rights. We have kin there – The Turkish Republic of Northern Cyprus (TRNC)."

The TRNC, established in 1983 on the northern third of the island, is only recognized by Turkey and faces a longstanding embargo in commerce, transportation and culture.

Meanwhile, the Greek Cypriot Administration enjoys recognition by the international community as the Republic of Cyprus, established in 1960, and is a member of the EU. The president once again voiced his determination to pursue and protect the rights of the TRNC, saying, "We will protect the law and rights of our kin here."

The president further indicated that some are putting forth inaccurate statements claiming that Turkey is violating international maritime law. "Turkey knows well what maritime law is and where international law comes into existence. As long as Libya’s official government stands upright, this step will be carried out," he said.

Turkey and Libya signed a deal last week after a meeting between Erdoğan and the head of the Presidential Council of Libya's U.N.-backed Government of National Accord (GNA), Fayez Al Sarraj, in Istanbul. The deal enabled Turkey to secure its rights in the Mediterranean while preventing any fait accompli by other regional states.

However, Greece, one of the main regional actors, did not welcome the deal and regarded it as a violation of its rights, though international law deems otherwise.