There are no plans to drop charges against or apologise for the arrest of Indian diplomat Devyani Khobragade, US sources are quoted as saying in Indian media reports.
The reports say prosecutors are gathering more evidence ahead of a 13 January deadline for her indictment.
Her detention on visa fraud charges and underpaying her housekeeper has led to a diplomatic row and outrage in India.
She denies all the charges and has been released on bail.
India has demanded an apology from the US over her alleged "humiliation".
But Press Trust of India news agency quoted US sources in New York as saying that the US is gathering more evidence against the diplomat ahead of 13 January, the deadline for her indictment.
Ms Khobragade, India's deputy consul general in New York, was arrested in the city on 12 December on suspicion of visa fraud and making false statements, after being accused of paying her Indian maid below the US minimum wage.
She was handcuffed and strip-searched after a complaint from the maid, Sangeeta Richard.
The diplomat, who has been released on bail, denies all the charges and has in turn accused Ms Richard of theft and attempted blackmail.
Delhi had already ordered a series of reprisals against the US.
Security barricades around the US embassy in the city were removed and a visiting US delegation was snubbed by senior Indian politicians and officials. India is also checking the tax status of Americans working at schools in the country.