BATAMDA, Egypt — One place to begin to understand why this parched country has nearly ruptured relations with its upstream neighbors on the Nile is ankle-deep in mud in the cotton and maize fields of Mohammed Abdallah Sharkawi. The price he pays for the precious resource flooding his farm? Nothing.

“Thanks be to God,” Mr. Sharkawi said of the Nile River water. He raised his hands to the sky, then gestured toward a state functionary visiting his farm. “Everything is from God, and from the ministry.”

But perhaps not for much longer. Upstream countries, looking to right what they say are historic wrongs, have joined in an attempt to break Egypt and Sudan’s near-monopoly on the water, threatening a crisis that Egyptian experts said could, at its most extreme, lead to war.

“Not only is Egypt the gift of the Nile, this is a country that is almost completely dependent on Nile water resources,” said a spokesman for the Egyptian Foreign Ministry, Hossam Zaki. “We have a growing population and growing needs. There is no way we can accept this kind of threat.”