Royal Bank of Scotland (RBS.L) is winding down its Greek operation and is putting its $5 billion shipping loans portfolio up for sale as the group scales back non-core activities, finance sources familiar with the plans said on Friday.

The move, part of a wider strategy by RBS to shrink parts of its international business, comes as Greek Prime Minister Alexis Tsipras makes a last ditch effort to secure a bailout from international creditors and prevent a financial meltdown in the country.

For decades, RBS has been a top lender to the global shipping industry and its Greek office - with an estimated 60 staff members - has played a pivotal role.

"We won’t be around for much more in Greece. RBS is slowly closing up operations here," one source at RBS said.

"The shipping business is up for sale. They have decided to sell it, if there is a buyer by December."

RBS is downsizing its corporate and institutional banking business in the Middle East, Africa, parts of Europe and Asia as the lender, majority owned by the British government, focuses on its home market.

British state-backed rival Lloyds Banking Group (LLOY.L) has also been exiting the ship finance sector and sold $500 million from its remaining ship finance portfolio in April last year, sources told Reuters. Pricing on that deal was in the region of 80 percent of the value of the loans, one of the sources said at the time.

Greek ship owners are among the country's wealthiest tycoons and the sector has been a major market for shipping banks despite tough conditions.

The Greek fleet, which includes Greek and foreign-flagged ships, is one of the biggest in the world and provides vital income for the country.

"This is a sad time for the ship finance industry when one of the market leaders for decades will seemingly no longer be with us (in Greece),” a finance source said.

Shipping still faces a multi-billion dollar funding hole as many European banks have retreated from the sector, partly due to capital constraints and regulatory demands to shore up reserves in the wake of the 2008 financial crisis.

RBS’s former shipping boss Lambros Varnavides, one of the industry's most influential players who retired last year, helped the bank to build a particularly strong presence inGreece.

While Greek shipping magnates generally operate from the Athens suburbs and the port of Piraeus, their companies are largely registered in places like the Marshall Islands and the Turks & Caicos. The firms are often listed on stock exchanges abroad and their ships fly foreign flags such as Liberia's. Given the international nature of their business, top Greek ship owners have been largely unaffected by the country's crisis.

The finance source said RBS's shipping loans portfolio in Greece was worth $5 billion. The bank had an estimated further $6 billion of loans in the rest of its global shipping book.

The remaining $6 billion of shipping loans were expected to be managed out of the UK, the source added.

RBS, which briefly became the world's biggest bank after an acquisition binge under former chief executive Fred Goodwin, has undergone a complex restructuring to focus on lending to British households and businesses.