ADDIS ABABA, May 7 (Reuters) - Eritrean opposition groups meeting in Ethiopia on Wednesday said they had agreed to join forces and launch a popular uprising in their Red Sea state.

The groups, brought together in the Eritrean Democratic Alliance, urged Eritreans abroad to help them forge a "truly national movement" to overthrow President Isaias Afwerki.

"The 13 Eritrean opposition groups have settled their differences and adopted a charter which would help us launch a popular uprising," Habte Tesfa Mariam, chairman of the Alliance's congress, told reporters.

Eritrean officials could not immediately be reached.

Tensions are rising between Ethiopia and Eritrea, which fought a 1998-2000 border war that killed 70,000 people. Both nations routinely accuse each other of supporting rebel groups.

Habte said that if the Alliance came to power, it would resolve the border dispute with Addis Ababa through dialogue. (Reporting by Tsegaye Tadesse; Editing by Daniel Wallis) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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