Yamaha said on Sunday it will not participate in next weekend's Qatar MotoGP, citing "the situation in the Middle East".
Diplomatic efforts to end the Middle East war have been punctuated by repeated threats from the United States and Israel to resume bombardments of Iran.
The war began on February 28 with joint US-Israeli strikes on Iran, which retaliated by targeting, among others, Gulf countries allied with Washington.
Yamaha issued a statement after Sunday's Malaysian MotoGP saying they would not be taking the risk of going to Qatar.
"Yamaha has not identified sufficient grounds to change its existing company-wide travel restrictions," the Japanese manufacturer said.
Yamaha's riders are France's Fabio Quartararo, the 2021 world champion, and Spaniard Alex Rins.
Australia's Jack Miller, who rides for the Japanese operation's satellite team Yamaha-Pramac, will have been happy with the decision as he made clear his reluctance to travel to Qatar just before Yamaha issued their statement.
"I have no desire to go," said Miller.
"Just like everyone else. There are 19 (out of 22 riders) who do not want to go there.
"I do not think we should ride in those conditions. We have been very clear about our position," added the 31-year-old, who has won four MotoGP's during his career.
The MotoGP Group said it was "disappointed" by the decision and said that "Yamaha's non-participation also carries sporting implications".
"While we recognise the team is subject to a broader corporate policy restricting travel to the Middle East, we do not believe this decision reflects the extensive assurances provided to all championship stakeholders," it said.
MotoGP said talks with Qatari organisers and safety advisers had not flagged any reasons to change plans for the event.
"We communicated that position, together with the latest available information, to all manufacturers and teams today and welcome the confirmation from the remainder of the grid that they will compete in Qatar, and we thank them for that commitment," the MotoGP Group said.
There are just three races left in the season, starting in Qatar.
Ducati's reigning seven-time world champion Marc Marquez won the race at Sepang and could clinch the title in Doha.
According to reports, there was haggling behind the scenes in Sepang about whether teams would go to Qatar and it has been reported that anyone who did swerve next weekend's race would be penalised.
'STANDING THEIR GROUND'
Sporting events in the Gulf have been affected by both the conflict with Iran and Saudi Arabia's clashes with the Houthis in Yemen.
In recent weeks, Houthi attacks on Saudi civilian infrastructure have reached a scale unprecedented since the start of the conflict in Yemen in 2014.
The Dakar Rally, which Saudi Arabia has hosted since 2020, was the latest competition to be moved, Portugal and Morocco will host the 2027 edition.
However, the world super-middleweight title fight between Mexican legend Saul 'Canelo' Alvarez and Frenchman Christian Mbilli did go ahead in Riyadh on Saturday, with the former reclaiming his crown.
The latter was a rare example of sports organisers standing their ground.
An exhibition tennis tournament due to feature Novak Djokovic, Carlos Alcaraz and Alexander Zverev has been postponed until late December.
The WTA Finals were also scheduled to be held in Riyadh this month but will instead take place at Indian Wells in the US.
This season's Formula One Grand Prix in Jeddah was cancelled, while the race in Bahrain was called off and later rescheduled under the same name in Malaysia.
The final round of the World Rally Championship in Saudi Arabia in November has also been scrapped.
The last two races of the F1 season in Qatar (November 29) and Abu Dhabi (December 6) are still on the calendar, but they are the subject of intense internal debate.