A rural pressure group warns that parts of mid Wales are in danger of becoming 'no go areas' for the Army.
The Army has been training on private land in Wales for decades
The Country Land and Business Association (CLA) said many landowners may prevent troops from using their fields because of the new hunting law.
The CLA's chairman Ross Murray said a senior officer had even spoken of the difficulties facing the military.
However, the Army said soldiers would train outside the country if they were stopped from using private land.
In October, a major Army exercise in Wales went ahead as planned, just weeks after farmers threatened to ban troops.
They said they would refuse to cooperate with the Cambrian Patrol in protest at the hunting legislation.
But the Army reminded landowners that they had given written consent for troops to use their fields and many had even been paid. They were forced to retreat over the issue.
Mr Murray, a former soldier and the new chair of the CLA in Wales, said he had spoken to one senior officer in Brecon, who said that obtaining landowner support was "now virtually impossible".
Mr Murray said: "Military training in Wales relies on the use of farmers' land and there are signs of withdrawal of support. The Army may have to go elsewhere.
"Relations between the military and the farming community have been put under unnecessary strain by the ban. Government ministers have forgotten that the lambing season is about to start."
He added: "Farmers feel that there has been a total loss of goodwill from the Government.
The Army will train outside Wales if permission to use land is withdrawn
"Every year land is made available to the military, almost entirely free of charge. So unhappy is the farming community in mid Wales over the Westminster hunting ban that support for next April's traditional escape and evasion exercise is likely to evaporate."
More that 2,000 individual landowners across 800 square kilometres in mid Wales have the power to stop next April's exercise.
David Webb, spokesman for the Army in Wales, said: "We are aware of the view of landowners and we've just had a very successful exercise called Cambrian Patrol.
"It's their (the landowners) decision and it's their land, but we can exercise on land not owned by individuals such as land run by national parks and the Forestry Commission.
"It's far too early to say what's going to happen until we test the water, but exercises could move outside Wales if the Army is prevented from using private land."
Mr Murray used the Royal Welsh Winter Fair on Monday to call on the Welsh Assembly Government to use secondary legislation to allow a licensed hunting system in Wales.
But Countryside Minister Carwyn Jones said the new hunting law was not a devolved issue.