BOGOTA, Aug 14 (Reuters) - Colombia's majority state-owned energy company Ecopetrol will agree a loan worth up to $4 billion with international banks to fund its purchase of the government's majority stake in the conglomerate ISA.

Ecopetrol signed a deal with Colombia's finance ministry on Wednesday to buy the government's 51.4% stake in ISA for 14.2 trillion pesos ($3.7 billion).

Now, the company has received authorization from the ministry to secure the loan with international banks Banco Santander, Citibank NA, JPMorgan Chase NA , and the Bank of Nova Scotia, Ecopetrol said in a statement late on Friday.

The loan, which will see 25% participation from each bank, is to be repaid within two years of signing the contract, and will include interest based on the three-month Libor rate, plus 80 basis points, with an initial aggregate commission of 30 basis points, Ecopetrol said.

Ecopetrol is Colombia's largest company. It produces most of the South American country's oil and owns the two most important refineries, as well as most of the pipeline network.

ISA owns operations in energy, roads, and telecommunications in Colombia, Brazil, Chile, Peru, Bolivia, Argentina and Central America through 51 affiliates and subsidiaries. ($1 = 3,830.25 Colombian pesos) (Reporting by Oliver Griffin; Editing by Daniel Wallis)