Ms Khobragade was arrested in New York earlier this month before being granted bail. Sources said that more evidence is being collected against Ms Khobragade to present before January 31, the deadline for the equivalent of a chargesheet to be presented in court.
Her case has forged a huge diplomatic dispute between the two countries. New Delhi, which wants Washington to drop the case and offer an apology, has retaliated by drastically pruning the privileges extended to US consular staff in India.
Ms Khobragade, 39, who was India's deputy consul general at its mission in New York, has been accused by the US of underpaying and overworking her housekeeper, an Indian named Sangeeta Richards. The US says the diplomat lied in a visa application about Ms Richards' salary, who does not get minimum wage.
India was enraged by Ms Khobragade's public arrest and consequent strip-search and said that the diplomat was entitled to immunity, an argument rejected by the US
Ms Khobragade's lawyer recently claimed that the US misconstrued the contentious visa application by interpreting Ms Khobragade's salary as that of her housekeeper's. The US has also refuted that charge.
India is trying to secure full diplomatic immunity for Ms Khobragade by shifting her to its UN mission in New York, although such a move needs the US State Department approval.
If that clearance comes through, the case against Ms Khobragade will be suspended for the duration of her assignment at the UN mission, but after that, she could be prosecuted.