Fiat shares lower after union health trust demands on Chrysler

A company logo is seen on a Fiat car displayed on media day at the Paris Mondial de l'Automobile, September 28, 2012.

MILAN (Reuters) - Shares in Italian carmaker Fiat (FIA.MI) were lower in early trading on Tuesday after a union health trust said the Italian company must more than double its offer for a 3.3 percent stake in Chrysler Goup it wants to buy.

Fiat's offer of $139.7 million is "substantially below fair market value," the United Auto Workers-affiliated trust said in documents filed in Delaware's Court of Chancery.

Fiat must pay at least $342 million for the stake, the UAW trust said in its response, which came nearly two months after Fiat sued the trust for failing to sell the shares.

Fiat declined to give a comment.

At 0815 shares in Fiat are down 0.7 percent at 3.36 euros.

(Reporting by Francesca Landini, editing by Stephen Jewkes)