One of the nation’s leading building trades unions is stepping up pressure on House Democrats who oppose the Keystone XL pipeline, calling on union members in 27 congressional districts to punish their representative in the midterm election.

A letter distributed by the Laborers’ International Union of North America (LIUNA) to the 27 districts calls for union members to make sure their representative “feels the power and the fury of LIUNA this November,” The Hill reported.

“Your member of Congress is trying to destroy job opportunities for our LIUNA brothers and sisters,” read the letter signed by Terry O’Sullivan, the general president of LIUNA, and obtained by The Hill on Friday.

“For every action, there is a reaction, and our reaction to this frontal assault on our way of life needs to be loud and clear. If you do not stand with us, we sure as hell will not stand with you,” O’Sullivan wrote, citing the jobs Keystone would create.

The House members being targeted by the union include Reps. Frank Pallone Jr., D-N.J.; Anna Eshoo, D-Calif.; Raúl Grijalva, D-Ariz.; and Tim Ryan, D-Ohio. All of the representatives signed a letter to Secretary of State John Kerry in March urging him to reject the pipeline.

The letter to union members asks them to remember that “unemployed construction workers desperately need the work” generated by Keystone XL, calling it a “lifeline” for thousands of members, according to The Hill.

Read More: