Finance minister Arun Jaitley unexpectedly left for the US for a medical check-up following a kidney transplant last year, sources said.

Jaitley, 66, who had a kidney transplant operation and follow-up check-ups at AIIMS last year, left for the US on Sunday night for a 'regular medical check-up', sources said without indicating when he would return.

This is Jaitley's first overseas visit since his kidney ailment was confirmed in April last year.

The minister was supposed to be a keynote speaker at the 7th C.D. Deshmukh Memorial Lecture organised by National Council of Applied Economic Research (NCAER) on Tuesday evening.

Jaitley, who was last week named the publicity head of the BJP's election team, is to present the BJP-led NDA government's sixth and last budget on February 1, before the general elections due by May.

Though it is supposed to be an interim budget, seeking Parliament nod for government spending for the first four months of the 2019-20 fiscal year beginning April, it is widely expected that his speech would be a full-length budget speech.

The new government will present the budget for the fiscal in July.

Jaitley had on May 14, 2018, undergone a renal surgery and was out of the finance ministry for nearly 100 days. During this period, railway and coal minister Piyush Goyal was given additional charge of the finance ministry.

He had stopped attending office at the beginning of April 2018 and had even cancelled a scheduled attendance at the 10th India-UK Economic and Financial Dialogue in London.

Jaitley returned as finance minister on August 23, 2018, and during the next few months limited public interaction to ward off any infection.

He has been the finance minister in the Modi government right from the time it took office in May 2014. He, however, was a minister without a portfolio between May 14, 2018, and August 23, 2018.

A Rajya Sabha MP since 2000, he was re-elected to the Upper House from Uttar Pradesh in March this year. He is also the leader of the House.

Jaitley had undergone a bariatric surgery soon after the BJP government came to power at the Centre in 2014. The surgery, to treat weight gain that he suffered because of a long-standing diabetic condition, was first performed at Max Hospital, but he then had to be shifted to AIIMS because of complications.