Argentina says it will ask the International Sea Tribunal, based in Germany, to intervene in the dispute over its navy ship impounded in Ghana.

Foreign Minister Hector Timerman said Ghana must free the Libertad by Tuesday if it wants to avoid such an action.

The ship was stopped from leaving Ghana last month following a local court order obtained by a US hedge fund.

The fund, NML Capital, argues it is owed $370m (£231m) as a result of Argentina's debt default a decade ago.

It is seeking $20m in return for the release of the ship, a three-masted training vessel.

Argentina has vowed not to bow to what it calls "blackmail by vulture funds". Holding out

The Libertad has been detained in the main seaport town of Tema since 2 October. Only a skeleton crew remain after more than 300 sailors flew home about three weeks later.

Sailors on board the Libertad reportedly pulled guns on Ghanaian officials last week after they tried to board the vessel to move it to another berth.

Water and electricity had reportedly been shut off to the ship a few days earlier in response to Argentina's refusal to let officials move the ship to a less busy part of the port.

NML Capital is a subsidiary of US hedge fund Elliot Capital Management, one of Argentina's former creditors.

In 2001 and 2002, Argentina defaulted on more than $100bn of debt.

Most of these loans were subsequently restructured, giving creditors about 30% of their money back.

However, some creditors including Elliot chose to hold out, pursuing the Argentine government through the courts.