Cairo fears that Ethiopia's Grand Renaissance dam project could diminish its water supply.
"This will be a crucial and definitive meeting on a global solution to this issue about the dam," said Sudanese Water Resources and Electricity Minister Muattaz Musa Abdallah Salim, hosting the Khartoum talks.
Despite two previous tripartite meetings late last year ending without agreement, Ethiopian Water Minister Alemayehu Tegenu said Monday the dam project would not have major consequences for Egypt and Sudan downstream.
His Egyptian counterpart, Hussein Mohamed al-Mughazi, stressed his country's "special situation because it depends totally on the waters of the Nile", a river that it also vital to Sudan.
Egypt has constantly expressed its opposition to any project that might disrupt the flow of the Nile.
The Blue Nile joins the White Nile at Khartoum to form the Nile, which flows through Sudan and Egypt before emptying into the Mediterranean.
Ethiopia began diverting the Blue Nile in May last year to build the 6,000 MW dam which will be Africa's largest when completed in 2017.
Ethiopian officials have said the project to construct the 1,780-metre-long and 145-metre high dam will cost $4.2 billion (3.2 billion euros).
Egypt believes its "historic rights" to the Nile are guaranteed by two treaties from 1929 and 1959 which allow it 87 percent of the Nile's flow and give it veto power over upstream projects.
Most other Nile Basin countries contest this.
A new deal signed in 2010 by other Nile Basin countries, including Ethiopia, allows them to work on river projects without Cairo's prior agreement.
In protest against the 2010 pact, Cairo withdrew from the Nile Basin Initiative (NBI), a forum for riparian countries to discuss joint management and development of the region's resources.