The states are locked in a long-standing row over the waters of the Cauvery river - a holy river for Hindus.

The chief ministers of the two states will be among those to attend.

Tamil Nadu is seeking the immediate release of three billion cubic feet of river water from Karnataka's storage dams. The Tamil Nadu authorities say that rice crops in the state are withering because of the water shortage.

Karnataka, where the Cauvery rises, has refused, saying a shortfall in monsoon rains has led to an acute water shortage for its own farmers.

Experts

Water Ministry Secretary Hassan: Leading team to assess reservoir levels

On Sunday Mr Vajpayee sent a team of experts to investigate reservoir water levels in the two states.

The team is expected to report to Wednesday's meeting in Delhi.

Analysts says the wrangling over the river water has embarrassed Mr Vajpayee's Hindu nationalist Bharatiya Janata Party, which had been claiming a river accord between the two states last year as one of its major achievements.

Top officials from both states held emergency talks last week to resolve the row, but failed. The premier then said he would take time off his election campaign to attend Wednesday's meeting.

Under an agreement reached earlier this year, the state should release about 200bn cubic feet of water to its neighbour every year.