DUBAI - GEMS Education, an international education firm headquartered in Dubai, plans to raise a loan of over $1 billion to refinance some existing debt before a planned initial public offer of shares in London, sources familiar with the matter said.

The company, backed by Dubai-based Fajr Capital, Bahraini state investment fund Mumtalakat and private equity giant Blackstone BX.N , is expected to issue a request for proposals to banks by the end of this month, said one of the sources, adding that the loan could go up to $1.2 billion in size.

A spokesman for GEMS declined to comment.

The private education provider will reshuffle some of its existing borrowings in preparation for its foreign IPO. "They're streamlining their corporate structure," one banker said.

GEMS, which operates more than 250 schools across 14 countries, could obtain a valuation of around $4 billion, some bankers estimate.

Among its borrowings, the company raised a $250 million, three-year loan in 2016 and borrowed 3 billion dirhams ($817 million) in 2015.

The new debt facility is expected to be split into conventional and Islamic tranches, and will most likely be led by UAE banks, said one of the sources.

(Editing by Andrew Torchia) ((Davide.Barbuscia@thomsonreuters.com;))