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LONDON, July 15 (Reuters) - Price guidance on a $1.5-billion bond by Colombian state-controlled oil company Ecopetrol ECO.CN(EC.N: Quote, Profile, Research) is expected to be around 400-425 basis points over U.S. Treasuries, sources said on Wednesday.

"The book has gone out at $3 billion. This is a very rare issuer," said one London-based fund manager.

Barclays Capital and JPMorgan Chase & Co, arrangers of the 10-year deal, could not be reached for comment.

The borrower completed a roadshow on Wednesday that was scheduled to take in New York, Boston, Los Angeles, San Francisco and London.

Proceeds of the deal will be used to fund Ecopetrol's investment plans.

Ecopetrol is rated "BB-plus" by Fitch Ratings with a stable outlook. (Reporting by Sebastian Tong; Editing by Padraic Cassidy)