A major Army exercise in Wales will be relocated if farmers carry out a threat to ban soldiers from training on private land.
The Cambrian Patrol began in 1959
Chairman of the Federation of Welsh Packs, Ken Jones, said he will prevent his fields being used by troops, in protest at the ban on hunting with dogs.
Hundreds of international soldiers take part in Cambrian Patrol in mid Wales.
It has tested soldiers' endurance and patrolling skills since 1959.
In previous years hundreds of troops from Britain, the Netherlands, Italy, Belgium, the US and Canada, have taken part.
Held over nine days at the end of October, soldiers use land in and around the Cambrian Mountains from Tregaron to Llantwryd Wells.
David Webb, a spokesman for the Army in Wales, said: "We acknowledge and appreciate the support we've received from farmers over many years.
"We very much hope that they will kindly give us permission to continue to use the land for Cambrian Patrol.
"If sufficient numbers of farmers withdraw their permission alternative arrangements will have to be made, but the exercise will go-ahead regardless on land that we have permission to use.
"We don't know at this stage where it will be re-located, but we will consider all options."
Mr Jones, 55, from Bwlchau Farm, near Llanwrtyd Wells, farms 800 acres with his wife, son and two daughters. He is also the master of Irfon and Tywi Hunt.
"Our gripe is not with the Army, but with Tony Blair and his Government.
"We've had an excellent relationship with the Army in the past and if the Government sees sense then this relationship will continue.
"We intend to cancel the Cambrian Patrol and permission will be withdrawn forever to use our land unless the Government changes its mind.
"The SAS has trained up here in the past too."
Dai Owen, 60, the master of the Gogerddan Hunt on the west side of the Cambrian Mountains, near Tregaron, said he will not allow the exercise to be carried out over his a 4,000-acre hill farm at Tynddol either.
"I have nothing against the military and this decision goes against the grain because I can remember soldiers coming up here since I was a kid," Mr Owen said.
"We've sheltered no end of soldiers from the bad weather when they've run out of energy.
"But the politicians don't care about us and every landowner in the hunt will continue to ban the Army until something changes."
Hundreds of troops from around the world take part in the Cambrian Patrol
Mr Owen said it would only take a handful of farmers to withdraw before the exercise would cease to be viable.
Meanwhile, the Farmers' Union of Wales said many of its members were threatening to refuse the Army access to their land too.
Union president Gareth Vaughan said: "We have had numerous telephone calls from angry farmers who are all threatening to stop the Army from using their land in retaliation for the hunting ban.
"They see it as the only weapon they have at their disposal to strike back at a Government that is not listening to their views."
The FUW said the ban would "seriously affect the military's training schedules."