SAO PAULO, March 18 (Reuters) - Brazil on Wednesday

named major companies the government has fined in recent months,

saying they did not comply with minimum freight price rules and

that continued non-compliance could see them barred from

contracting freight services.

The fines come as the government pledged to tighten

enforcement of rules to appease truck drivers, after unions

began advocating for a strike this week following a jump in

diesel prices.

Transport minister Renan Filho named food processor MBRF

, fuel distributor Vibra, sugarmaker Raizen

, brewer Ambev ( ABEV ), grain trader Cargill and

consumer goods firm Unilever ( UL ).

Raizen in a statement said it calculates freight payments

based on fixed and variable components, and that the government

audit does not consider total freight paid.

Vibra voiced concern over its freight payments being

evaluated separately, saying it is aligned with market prices.

Unilever ( UL ) said the government does not take into account

market practices, and that it complies with regulations

throughout its logistics chain.

MBRF, Ambev ( ABEV ) and Cargill did not respond to emailed requests

for comment.