Deep-sea explorer Graham Jessop has defended an American couple's plan to marry on the deck of the Titanic.

Mr Jessop, recovery manager for the company RSM Titanic, said the $30,000 fee would go towards financing more scientific research.

David Leibowitz, 28, and Kimberley Miller, 27, will descend two-and-a-half miles to the sunken liner in the three-man Mir submarine Akademik Keldysh, owned by the Russians.

The sub will hover near the bow of the liner, where the ceremony will take place.

Mr Jessop, who is spearheading the recovery of historic artefacts from the Titanic, used the same vessel to explore the liner before the recovery operation began.

Mr Jessop, formerly of Keighley, is the son of Keith Jessop, who recovered gold bars from the sunken HMS Edinburgh in the 1970s.

Graham said: "The submarine has to be hired out for tourist work in order to help finance its continued scientific work.

"It will be an adventure for this couple. The Titanic is a beautiful sight -- one of the wonders of the world - and is relatively untouched. And if you're into deep-sea diving, this is the ultimate dive."

"I believe that if good things can come out of these tourist trips they are worthwhile, and it will obviously make this couple very happy."

He said the only drawback was that there were no toilet facilities in the sub and when he went down the round trip took 12 to 14 hours.

"It takes two-and-a-quarter hours to get down and an-hour-and-a quarter to get back to the surface," he added.

There is no room in the Mir to stand up, but Mr Leibowitz, a computer expert, is hoping to be able to go down on one knee to propose.

The couple decided on the wedding after Mr Leibowitz won an Internet contest for a chance to dive on the wreck, which sank after hitting an iceberg in April 1912.

They hope to reach the bow to recreate the scene from the movie Titanic, in which lovers Jack and Rose, played by Leonardo DiCaprio and Kate Winslet, imagine they are flying.

No decision has yet been made on who will marry them -- either the pilot or by two way intercom with the surface.

The plan has sparked controversy and Brian Ticehurst of the British Titanic Society said: "I have no objection to people going down to view the wreck.

"But to use the ship where over 1,500 people died for a gimmicky wedding like this is just wrong."