The 25-year-old Great Britain Rugby League international becomes the latest high profile player to move to the 15-man code.

"It is a great day for me," he said. "It is something I've talked about for a long time, but now is the right moment.

"I am under no illusions, I have a tough, hard road ahead.

"It is going to be difficult for me to break into the Cardiff side and I don't want to look any further forward than that."

Leeds will receive �850,000 and a hospitality box at the Millennium Stadium for Harris while a large chunk of the �2m will be used to pay the player's wages.

"I welcome Iestyn with open arms," said Welsh national coach Graham Henry. "This is a hugely significant day."

Harris, who qualifies for Wales through his father and grandfather, will link up with Cardiff in September and is expected to make his international debut against Tonga at the Millennium Stadium in November.

"Naturally we are disappointed to be losing Iestyn," said Leeds chief executive Gary Hetherington.

"He has been a terrific servant to the club and to the game, but we fully understand his desire to continue his career with the Welsh Rugby Union and Cardiff.

"We have tried to negotiate a deal which will reflect his standing and ability in the game."

The four-year deal breaks the transfer record set in 1996 when Newcastle Falcons paid Wigan �750,000 over five years for Va'aiga Tuigamala.

In four years at Headingley he has played in a variety of positions - full-back, stand-off and scrum-half - but still clocked up more than 50 tries in 131 appearances.

He joined Warrington in 1993 where he came under the wing of dual-code international Jonathan Davies, and topped 500 points before being lured to Leeds.

Harris joins other rugby league stars such as Jason Robinson and Henry Paul who have switched codes in recent times.