Congress president Sonia Gandhi on Tuesday left for the United States for a medical check-up required after a secret surgery she underwent in August.

The party sources said there is nothing to worry as she campaigned in the Assembly elections all these days. They said she will be back in Delhi before the counting of votes begin.

She has travelled abroad for what the party described as "a routine check-up." Congress chief spokesman Janardan Dwivedi said she is expected to return in "4-5 days."

But the party refused to disclose the current status of Sonia's health. It is suspected that she was suffering from cancer and had gone for a surgery at the Sloane-Kettering Cancer Centre in New York in August.

It is not confirm whether her daughter Priyanka or son Rahul have accompanied her.

Sonia has gone on a short trip as stressed by Dwivedi because she has not constituted a core team to manage the party affairs.