The sale of key assets in distressed US auto maker Chrysler to a consortium headed by Fiat of Italy will be completed on Wednesday, a Fiat spokesperson said.

"The finalisation of the operation will take place early in the morning US time," the spokesperson said.

An obstacle to the transaction was cleared on Tuesday when the US Supreme Court lifted a freeze on a deal to save Chrysler from liquidation via an alliance with Fiat.

Late on Tuesday, the nine-member court late reversed the freeze, introduced by Justice Ruth Bader Ginsberg the previous day, which had given justices time to weigh complaints from Chrysler investors who said they would be short-changed and their rights trampled by the Fiat deal.

In a two-page order, the court said the disgruntled investors — a group of Indiana pension funds — had failed to show "that the circumstances justify" the stay placed on a lower court's approval of the deal.

Italy's Fiat, one of Europe's biggest auto makers, is now expected to take an initial 20-percent share in Chrysler in return for sharing technology that can be used to build, smaller, more fuel efficient cars.

The United Auto Workers union will hold 55 percent of Chrysler and the US and Canadian governments 10 percent.

Fiat could gradually boost its interest to 35 percent and would have an option to take control of the group from 2013.

Fiat boss Sergio Marchionne will head the new-look Chrysler.

Shares in Fiat jumped 3.84 percent to 7.715 euros as of 9.45am on the Milan stock market in overall trading that was up by 1.55 percent.