(REUTERS) - Eight-division world champion Manny Pacquiao's proposed fight against Britain's former world light-welterweight champion Amir Khan has been postponed, according to the Filipino's promoter, Bob Arum.

The 38-year-old Pacquiao and Khan, 2004 Olympics silver medallist, tentatively agreed to an April fight in the United Arab Emirates before negotiating a change of date to May 20.

Arum, however, told the Los Angeles Times that the US$38 million (S$53 million) offer for the bout had failed to materialise and that the duo could not face each other until the second half of 2017, under revised terms.

"Manny wanted to roll the dice. He rolled the dice and it came up snake eyes (double one)," Arum said of the World Boxing Organisation (WBO) world welterweight champion.

"That deal is done for now."

Arum said Pacquiao's advisor Michael Koncz would deliver a revised proposal for a fight against an alternative opponent that could be staged in July.

"Koncz will meet with Manny, and if he accepts it, we'll go ahead. If he doesn't, there's nothing we can do," Arum added.

Pacquiao (59 wins, 6 losses, 2 draws) claimed the WBO title with a unanimous points victory over American Jessie Vargas in Las Vegas last November, while the 30-year-old Khan (31 wins, 4 losses) has not fought since May 2016.

Khan made an audacious weight class move to middleweight to take on Canelo Alvarez but the Briton was knocked out by his hard-hitting Mexican opponent in the sixth round.