NEW YORK — The machinists union said on Wednesday it opposes a tentative labor contract reached this week with General Electric Co, potentially impeding the Boston-based conglomerate’s efforts to avoid labor unrest during a difficult period.

“Our recommendation is to reject,” Brian Bryant, general vice president of the International Association of Machinists and Aerospace Workers (IAM) told Reuters. “It’s what we consider a concessionary contract.”

The IAM, one of 11 unions representing 6,600 workers that would be covered by the deal, has workers in GE’s profitable aviation and health care businesses, not the power unit that has dragged down GE’s profits in recent years.

GE and leaders representing the unions reached the tentative four-year agreement on Monday, following 21 days of talks. The lead and largest union at GE, known as the IUE-CWA, can pass the agreement if 50 percent plus one member vote to approve it.

“We hope that the IUE will also vote it down and lead to more negotiations,” Bryant said.

GE said balloting is expected to take place by July 11. The contract provides $1.80 in wage increases over four years, no medical premiums increases in 2020 and $4,500 in cash payments.

Bryant said workers would lose some overtime they now receive when starting shifts early or staying late at jet engine factories.

Paul Lalli, head of labor negotiations at GE, said in a statement on Wednesday that the company had “achieved our goal of creating a fair deal that provides good wages and meaningful benefits for our employees while addressing the unique challenge we face today to return GE to a position of strength.”

The company was not immediately available to comment on the IAM decision.

IUE-CWA leaders said earlier this week that they endorse the contract and will recommend it to their members. IUE-CWA leaders did not respond to requests for comment on Wednesday.

GE has been laying off thousands of workers worldwide as it restructures in the wake of a $22.8 billion loss last year, caused largely by a write down in the power unit.

Among the unions covered by the agreement the IUE-CWA is the largest and the IAM is the second-largest. The agreement covers workers at facilities Massachusetts, Ohio, Kentucky, Kansas, New York and Wisconsin, GE said. — Reuters