Sources said Sikh organisations have been requesting with US lawmakers after the refusal by the army to let two Sikhs with turbans join active duty a few months ago.
Captain Kamaljit Singh Kalsi, a doctor, and Second Lieutenant Tejdeep Singh Rattan, a dentist, were told to remove their turbans by the military when they were about to enter active duty after completing their preliminary programme.
In their letter to Gates, the lawmakers said, "We do not believe that any American should have to choose between his religion and service to our country."
"We urge you to take all necessary steps to ensure that these two officers - and other Sikhs that may wish to serve - are able to maintain their articles of faith," lawmakers said.
Citing the example of Canada, Sweden and other countries where Sikhs are allowed to wear their symbols in the armed forces, Sikh organisations have urged Gates to end this discrimination by the US army.