Indian security agencies are said to have pushed for the break following revelations about the activities of David Headley, the US citizen with alleged links with the Lashkar-e-Tayyeba, who was arrested in October.
Investigations have shown that Headley was in and out of India repeatedly using tourist visas for two years before the 26/11 attacks in Mumbai last year, during which he reconnoitered many of the spots attacked by the terrorists on 26/11.

Details of precisely which categories of tourists will be affected, when and how, are not yet clear.

A message from the United States Mission in India to American citizens in the country on Wednesday, said: "The government of India is reviewing its regulations pertaining to the entry of American citizens holding long-term Indian tourist visas. To date, these new regulations are not finalized and are being implemented inconsistently."

"...It is clear that the rules will only affect those who wish to enter India on a tourist visa within two months of their last departure from India," it added.