The government had last month empowered the Army to procure ammunitions and other military hardware directly to maintain combat readiness for short-duration "intense wars" and the officials said the additional funds were sought to address its requirements.
The government had set aside Rs 2.74 lakh crore for the armed forces in the Union Budget and the Rs 20,000 crore has been sought in addition to that.
The officials claimed that the demand for the additional funds had nothing to do with India's standoff with China in Dokalam in the Sikkim sector.
They said the finance ministry had indicated that the demand for the additional funds would be considered "favourably" and "at the earliest".
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Union Finance Minister Arun Jaitley also holds the additional charge of defence.
In a major decision, the government had last month empowered the Army to procure critical weapons systems and military platforms directly.
According to the decision, the vice chief of the Army had been given the "full" financial powers to procure ammunitions and spares for 10 types of weapons systems and equipment after an internal review revealed that the optimum level of "war stores" was not being maintained.