NEW YORK (Reuters) - Marathon Petroleum ( MPC ) and the Teamsters union, which represents refinery workers in Detroit, Michigan, are at a standstill as negotiations for a new labor agreement stagnate and the strike at the plant enters its third week.

More than 200 Teamsters at Marathon's Detroit refinery called for an economic strike on Sept. 4 after nine months of pay- and safety-related negotiations and mediation with Marathon failed to reach agreement. The prior contract expired in January.

"Unfortunately, the parties have not reached an agreement," a Marathon spokesperson said.

Marathon representatives and the union had several negotiating sessions under a federal mediator, including this past Friday and Sunday.

"We continue to be in regular communication with the federal mediator; however, at this time, no additional negotiation meetings are scheduled."

Teamsters Local 283 represents 273 workers at the Detroit refinery, 95% of whom authorized the strike.

President of Teamsters Local 283 Steve Hicks said Marathon representatives walked away from the bargaining table at the latest round of contract talks this past weekend and canceled the negotiating session that was due this Friday.

The Detroit refinery started planned turnaround activities earlier this month.

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.