WASHINGTON (Reuters) - The International Monetary Fund said on Thursday its executive board approved a new three-year, $5.34 billion stand-by arrangement for Iraq to support Baghdad's efforts to deal with lower oil prices and ensure debt sustainability.The IMF said in a statement the approval will allow for the immediate disbursement of about $634 million under the programme. In July 2015, Iraq received about $1.24 billion under the previous rapid financing instrument programme. (Reporting By David Lawder; Editing by Chris Reese)