Congress president Sonia Gandhi left for the United States on Saturday for a routine medical check-up, sources close to her said.
They said her son and former Congress chief Rahul Gandhi is accompanying her during her travel to the US.
Rahul is expected to return within a week.
Gandhi, 73, is expected to be away for around a fortnight and will miss more than half of the Monsoon Session of Parliament.
Her medical check-up was overdue and was delayed due to the COVID-19 pandemic, they said.
The sources said Gandhi left for abroad early on Saturday and would return in the last week of September.
Congress chief spokesperson Randeep Surjewala tweeted, 'Congress president Smt Sonia Gandhi is travelling today onwards for a routine follow up and medical check up, which was deferred due to the pandemic.
'She is accompanied by Sh. Rahul Gandhi. We take this opportunity to thank everyone for their concern and good wishes.'
She had cleared the Congress' organisational restructuring before departing for her medical check-up.