"Too much delay is not good for us and for the owners of the tanker and the crew as well. We are not threatening them but we are urging them to be honest," he said.

Crew 'unhurt'

The pirates, who boarded the tanker on November 15, are looking for at least $15m in ransom payments to release the vessel, which is anchored off the Somali coastal village of Haradheere.

The hijackers are still in talks with the owners of the Sirius Star and the crew have not been harmed, Said said.

"We're treating the people on the ship very courteously and this will not change unless the other side behaves aggressively," he said.

Two British crew members said that they had not been hurt by the pirates.

"Everything is OK, we've got no mistreatment or anything, we're being treated quite well," Peter French, the vessel’s chief engineer, told ITV News television by telephone.

“Hopefully we are going to get some more phone calls to our families soon. Our families don't have too much to worry about at the moment."

James Grady, the vessel’s second officer, said that although members of the 25-strong crew are not being allowed on deck, their captors have not hurt them.

It not clear whether the crew members were in the immediate presence of pirates during the telephone interviews.

Countries including the US, Russia and India have sent naval ships to patrol waters around the Horn of Africa in an attempt to stop pirate attacks.

Their action comes as piracy threatens the safe passage of maritime cargo through the Gulf Aden, towards the Suez Canal.

Somali pirates are holding 17 ships and more than 250 crew members hostage, and have carried out more than 100 attacks in the last year.