Unions say some in the private sector may join the strike

Another 30,000 workers in 124 airports - opposed to privatisation plans - will also join in the day of action called by the United Forum of Bank Unions.

The All India Bank Employees Association (AIBEA), says mergers will shrink employment opportunities.

The finance ministry says state banks should merge to boost competitiveness.

'Social objectives'

"There's a need to expand branch network and not shrink them in the name of mergers," Kamal Bhattacharya, vice president of AIBEA told Reuters.

"The social objectives are being relegated to the background."

State-run banks control more than 66% of India's banking, however, although it is calling for mergers the government has said it will not privatise public sector banks.

It will also keep a majority stake in state banks, such as State Bank of India, Bank of India, Bank of Baroda, and Union Bank of India.

Private sector

The United Forum of Bank Unions is said to represents roughly 95% of the country's 1.3 million bank and insurance workers.

A previous stoppage in March saw one million workers go on strike, and it is predicted that some staff at private and foreign banks may also join the stoppage.

Union members are threatening to disrupt all services at airports, except air traffic control.

However state-run domestic carrier Indian Airlines does not expect any major disruptions.