DUBAI/DOHA (Reuters) - Qatar accused Saudi Arabia of “reckless behavior” that is tearing apart a pro-Western Gulf bloc in the wake of a report that Riyadh threatened military action against Doha in a stand-off between regional powers.

FILE PHOTO: A mosque is seen along a coastline in Doha, Qatar, June 15, 2017. REUTERS/Naseem Zeitoon/File Photo

The Qatari foreign minister said the threat -- reported to have been made in a letter from the Saudi king to France warning over a Russian arms deal with Doha -- aims to further destabilize the region after Riyadh and its allies imposed a political and economic boycott on tiny Qatar a year ago.

Saudi Arabia, the United Arab Emirates (UAE), Bahrain and Egypt accuse Doha of supporting terrorism - charges which it denies.

The dispute has evaded mediation efforts by Washington which has strong alliances with both sides and fears the split among Sunni Muslim U.S. allies could benefit Shi’ite Muslim Iran.

France’s Le Monde reported on Saturday that Saudi King Salman sent a letter to French President Emmanuel Macron warning the kingdom could act militarily if Doha goes ahead with a deal to buy Russian S-400 missile air defense systems.

“There is no serious military threat out of this (letter), but the way it is being used to justify or to create a disturbance in the region is just unacceptable,” Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani told the English-language channel of Qatar-based Al Jazeera.

“Aren’t they aware that the region has lost the Gulf Cooperation Council (GCC), the last united bloc in the Arab region,” he said in a separate comment on Twitter, referring to the 37-year-old political and economic Gulf alliance.

Doha is seeking confirmation from the French government about the letter, the minister said in the interview aired on Tuesday. He stressed Qatar’s sovereign right to independently decide on its defense procurements.

A European diplomat confirmed the letter had been sent to France as well as to the United States and Britain. French and Saudi state communications offices have not responded to requests for comment.

A Qatari official has been quoted as saying it was in talks to buy Russian S-400 missile air defense systems.

A Qatari foreign ministry spokeswoman said on Twitter on Tuesday that there are talks to hold a summit in Washington in September on the Arab row, which Abu Dhabi and Riyadh have said is not a high priority and must be resolved within the GCC bloc.

GULF CHASM

Western diplomats said neither side showed signs of backing down as the conflict entered its second year. “We tend to see the situation as hopeless and a new era in the region has begun which everyone has to accommodate,” one Western diplomat said.

Analysts say the row has failed to isolate Qatar which has moved to strengthen its energy and investment ties with the United States, Turkey, Russia and China. But it has widened cracks among GCC states.

“Ties of trust and confidence have been shattered on both sides of the divide as positions have hardened and a ‘zero-sum’ mentality has taken root,” wrote Kristian Coates Ulrichsen from Texas-based Rice University’s Baker Institute.

“Kuwaiti and Omani officials watch on, uneasily aware that they too could be vulnerable to regionally-assertive Saudi and Emirati pressure when they undergo eventual leadership transitions of their own,” he wrote in Gulf International Forum.

He said the powerful crown princes of Riyadh and Abu Dhabi were redefining Gulf politics around a “hyper-hawkish axis”.

The four boycotting states have issued an ultimatum that Qatar meet a list of demands, including closing Al Jazeera television and reducing ties with regional foe Iran. Doha says the boycott is an attempt to impinge on its sovereignty.

The boycott disrupted Qatar’s imports and triggered the withdrawal of billions of dollars from Qatari banks by depositors from the four states. Doha quickly moved to develop new trade routes and deployed tens of billions of dollars from its massive sovereign wealth fund to protect its banks.

The economy of tiny but wealthy Qatar, the world’s largest exporter of natural liquefied gas, has weathered the boycott and diplomats said Doha has no reason to bow to demands, especially as the emir has emerged stronger at home.

“We do not expect any more measures from Saudi Arabia and the UAE against Qatar as they have fired all their bullets. The crisis now is only about information and media war,” another Western diplomat said.