West Bengal Chief Minister Mamata Banerjee's eleventh-hour opposition to the Teesta River Water Sharing Treaty has stunned diplomats and experts on both sides of the border and threatens to unravel Prime Minister Manmohan Singh's first-ever visit to Bangladesh beginning Tuesday.

Ms. Banerjee's objection hours before she was to join Dr. Singh's entourage along with four other Chief Ministers could jeopardise the remaining “second generation” river water sharing agreements that were to ride on the back of the Teesta accord, said highly placed officials.

“Frankly, what West Bengal is saying makes no sense to me. This has been discussed for years now, and every concern of theirs had been addressed,” said a senior Water Resources Ministry official in Delhi. During their 40 years of co-existence, India and Bangladesh inked just one river water sharing pact and were poised to resolve issues on the other 50-plus rivers they share until Ms. Banerjee threw a spanner in the works.

In Dhaka, officials and political observers slammed Ms. Banerjee's theatrics as “abrupt, inappropriate and unfortunate,” saying the 48-52 apportionment of the disposable flow of the Teesta was finalised after a series of confabulations, of which she was aware.

Diplomats are now engaged in last-minute talks with their Bangladeshi counterparts to salvage other agreements that were part of a comprehensive package stitched up in a manner that while some addressed India's concerns, others took care of Bangladesh's anxieties.

Dhaka, being a lower riparian state, has a greater stake in river water sharing. It had hoped that the Teesta accord would lead to a similar agreement on the Feni river. In return for the relief that the “second generation” agreements would have provided to the rural populace hit alternatively by flood and drought, Dhaka was prepared to overlook domestic political opposition to providing transit access to India, Nepal and Bhutan.

Bangladesh officials remained tight-lipped on the issue and refused to comment on the prospect of signing the Feni river water sharing deal, which, too, was finalised and ready to be signed during Dr. Singh's visit.

Foreign Secretary Rajan Mathai told newspersons in New Delhi that no agreement on the sharing of Teesta river waters could be reached without West Bengal's consent. “In our federal system, nothing is done and nothing will be done without the consultation of the State government,” he said.

Mr. Mathai was unaware of the details of Ms. Banerjee's demands but said efforts were being made to resolve the eleventh-hour crisis. He noted that the Chief Ministers of Assam, Tripura, Meghalaya and Mizoram were travelling with the Prime Minister. “The presence of four CMs underlines the importance of the PM's visit and one more CM would have been useful,” he said.

Water Resources Ministry officials were perplexed by Ms. Banerjee's position, and argued that West Bengal would in fact gain substantively from the power generated from dams that will be built in Sikkim to deliver Bangladesh's share of water.

The Indian Constitution mandates that water is a State subject, giving West Bengal considerable leverage over the Teesta accord, but it gives the Centre a say in the matter.

Dr. Singh's visit is expected to see a number of agreements aimed at building relations, notably by granting Bangladesh freer access to the Indian market for its textiles to help reduce its trade imbalance. India also expects to sign a protocol on demarcating its long-disputed land border with Bangladesh.