Qatar's foreign minister told Al Jazeera he did not think the Saudi threat - reportedly made in a letter to France - was serious. But he accused Riyadh of using the letter to try and create a "disturbance" in a region already rocked by a year-long stand-off between Doha and other powers.
France's Le Monde newspaper reported on Saturday that Saudi King Salman had sent a letter to French President Emmanuel Macron expressing concern over talks between Doha and Moscow about Russian S-400 missile air defence systems.
The newspaper added that the king had said Saudi Arabia was ready to consider all measures, including military action.
"We are seeking formal confirmation from the French government (about the letter)," Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani told the English-language channel of Qatar-based Al Jazeera in an interview aired on Tuesday.
"There is no serious military threat out of this, but the way it is being used to justify or to create a disturbance in the region is just unacceptable," he said. "There is no legitimate grievance behind this letter and threatening Qatar."
Saudi Arabia, Egypt, Bahrain and the United Arab Emirates severed diplomatic and economic ties with Qatar a year ago, accusing Doha of supporting terrorism. Qatar denies the accusation and says the boycott is an attempt to impinge on its sovereignty.
The French president's office and the Saudi government's communications office have not responded to requests for comment on the newspaper report.
Asked if Doha would go ahead with the deal, the foreign minister said: "Qatar made all the options open for its defence procurement, so we are seeking the best quality to defend our country and we have all the options open for this."
Sheikh Mohammed described the Saudi move as "reckless behaviour".
Washington has strong alliances with both sides and fears the split among Sunni Muslim U.S. allies could benefit Shi'ite Muslim Iran.
Qatar hosts Al Udeid Air Base, which is home to more than 11,000 U.S. and coalition forces.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)