Mr Brunstad said his family's presence would give him strength

George Brunstad originally planned to make the 21-mile crossing on Wednesday, his 70th birthday, but had to postpone the attempt because of bad weather.

Mr Brunstad, who lives in Connecticut, is the uncle of the Hollywood star Matt Damon - currently starring in the box office hit, The Bourne Supremacy.

The retiree said he expected the crossing to take "at least 15 hours".

He went on to say that his family - who are crewing for him - helped give him strength.

Cold water

The oldest person to have swum across the Channel is Australian Bertram Batts, who made the crossing at the age of 67 in 1987.

If he is successful in his attempt, Mr Brunstad will become the first septuagenarian to achieve the feat and is expected to land at Calais at around midnight.

Speaking before he took to the water, he said: "For the first time I'm happy that I'm the oldest competitor".

His wife Judy Brunstad said she was feeling confident: "When he sets his mind to something, he usually achieves it - that's just the way he is and that's why I love him."

The 70-year-old expects the crossing to take at least 15 hours

A spokesman for the Dover Coastguard said Mr Brunstad was on course to make the swim.

Mr Brunstad, who retired as an American Airlines pilot in 1994, is an experienced long-distance swimmer who has won more than 100 national championship medals in US Masters Swimming.

To prepare himself for the Channel conditions, he has been training in the cold waters off the coast of Maine.

He has also been training for distance but says the farthest he has swum in a competition is 10 miles, while in training he has swum a distance of 14 miles.

Although the distance of the crossing is 21 miles, Mr Brunstad said the tides could make it the equivalent of 30 miles.