WASHINGTON, June 29 (Reuters) - The International Monetary Fund said on Tuesday its executive board has approved a $2.5 billion, 39-month Extended Credit Facility for Sudan after the country cleared $1.4 billion in IMF arrears to begin debt relief negotiations under the Heavily Indebted Poor Countries initiative. An IMF official told a news conference that the debt relief process, expected to take about three years, would ultimately reduce Sudan’s external debt burden to about $6 billion from the current level of about $56.6 billion, or about 163% of GDP. (Reporting by David Lawder, Editing by Rosalba O’Brien) Our Standards: The Thomson Reuters Trust Principles.