NEW YORK, Sept 5 (Reuters) -

Marathon Petroleum ( MPC ) has been unwilling to negotiate

with union members at its Detroit refinery since more than 200

workers went on strike, Teamsters said on Thursday, adding that

the industrial action could be extended to the largest U.S.

independent refiner's other plants.

Around 200 workers at Marathon's Detroit refinery

walked off the job

on Wednesday after months of pay- and safety-related

negotiations and mediation with Marathon did not yield results.

"We want to go back to the table but they are refusing

to bargain," said Steve Hicks, president of Teamsters Local 283.

Union members are fighting for higher pay, said Hicks.

The wage increases Marathon offered to union members, around 3%

each year, is not enough to keep up with inflation, Hicks said.

Members also want union security, he said. Michigan's

repeal of its

right-to-work law

, which had prohibited workers paying union dues as a

condition of employment in a unionized workplace, took effect in

February.

Teamsters could extend the strike to other Marathon plants

if negotiations continue to stagnate. "It's a big possibility,"

Hicks said.

The 140,000 barrel-per-day (bpd) Detroit refinery is one

of Marathon's 13 refineries with approximately 2.9 million bpd

of crude oil refining capacity.

Teamsters also represent workers at Marathon's

102,000-bpd Saint Paul refinery.

Marathon did not respond to requests for comment.