The duty of the Government to look after military personnel and veterans will be enshrined in law, Prime Minister David Cameron is expected to confirm.
Pressure to meet a pre-election commitment to formalise the military covenant commitment to the welfare of the armed forces and their families has been mounting over recent weeks.
Mr Cameron has faced claims that he was watering down the pledge after legislation promised only an annual Commons debate on how well the covenant was being respected.
Ministers are believed to be wary of the prospect of facing court challenges over failures if the legitimate expectations were made explicit on the statute book.
Tory backbench MP Philip Hollobone has tabled an amendment to the Armed Forces Bill which would grant formal recognition of the covenant - a potential focus for rebellion.
And the Royal British Legion has led other military charities and campaign groups in criticising the weaker provisions in the Bill. They have raised regular concerns that military personnel are failing to be provided with the level of service they are entitled to in areas such as health, housing and pay.
The Prime Minister and Defence Secretary have defended their position over recent weeks, insisting there were good reasons not to be overly prescriptive.
But defence minister Andrew Robathan, who is steering the Bill through the Commons, told The Daily Telegraph that the Government was "putting the military covenant on a statutory basis for the first time".
The legal definition is not expected to detail specific commitments about individual public services but will instead concentrate on broader principles - such as that no-one should be disadvantaged because of their military service and, beyond that, that special treatment could sometimes be justified.
Shadow defence secretary Jim Murphy said: "The Prime Minister appears to have finally done the right thing. If true, this is a retreat from an inevitable defeat in Parliament in the face of real anger from forces families and MPs."
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