Pakistan says it is seeking arbitration in a dispute with India over a controversial dam being built in Indian-administered Kashmir.
A Foreign Ministry spokesman said the World Bank had been asked to intervene.
He accused India of refusing to budge in talks on the dam, which Pakistan says breaches a shared water treaty.
India called the Pakistani move unjustified. The BBC's Paul Anderson in Islamabad says the dispute is bound to be a setback to peace talks.
The two sides met to discuss the planned dam in early January, but no progress was made.
'Inordinate delays'
The Baglihar dam and hydro-electric power project is being built by India over the Chenab river that flows from Indian-administered Kashmir into Pakistan.
"If India is not ready to demonstrate a spirit of accommodation for an issue which is very clear... how are they going to solve much harder issues like Kashmir?"
Islamabad says the dam will obstruct the flow of water into Pakistan.
It says the project violates a deal brokered by the World Bank in 1960 for sharing river water between the two countries.
Pakistan Foreign Ministry spokesman Masood Khan said India wanted to present the dam as a fait accompli.
"India has inordinately delayed the process... and pressed ahead with the construction of the dam in violation of the treaty, so we have taken the decision to approach the World Bank," he said.
Pakistan wanted the World Bank to appoint a neutral expert, he said.
India, meanwhile, insists work on the dam can proceed while wide-ranging peace talks which the two sides started last year continue.
Delhi insists that the project is "strictly within the parameters of the treaty". It says the dam will not store water or disrupt flows.
"We do not believe that a reference to the World Bank is justified," foreign ministry spokesman Navtej Sarna told reporters in Delhi.
Slow progress
Relations between the nuclear-armed neighbours have improved since last year's peace initiatives between Pakistani President Pervez Musharraf and the then Indian Prime Minister, Atal Behari Vajpayee.
A number of confidence-building measures have been introduced over the past year, including a resumption of rail, air and bus links and a strengthening of diplomatic ties.
But leaders have yet to negotiate the big obstacles to peace, in particular the dispute about divided Kashmir, over which the nations have fought two wars since independence.
Analysts say that will be the real test of the political will in both nations to find a solution.
Mr Khan said Pakistan's move should not affect the broader dialogue between the two countries.
But our correspondent says Pakistan and India have been riven by half a century of war, hostility and suspicion, and that might be wishful thinking.
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