Unionized janitors and building workers marched through downtown Washington streets during the Thursday evening rush for the second time in 10 days to draw attention to labor negotiations that officials say are far from over.

A labor contract that covers more than 11,000 Washington area cleaners with the Service Employees International Union is set to expire Oct. 15. If a new agreement cannot be reached before then, workers have threatened to strike.

Thursday’s demonstration — which included an address by D.C. Council member Brianne K. Nadeau (D-Ward 1) — began at 4:15 p.m. in Farragut Square. Workers clad in the union’s signature purple worked their way past cars and buses along K Street, then were to continue on 19th Street NW, march past the World Bank building and march onto Pennsylvania Avenue before circling up 17th Street toward the park.

“I stand behind janitors and 32BJ SEIU in their collective-bargaining efforts to get a fair contract,” Nadeau said in a statement released by the SEIU. “In order to give our working families a fighting chance, we must be creating jobs that provide living-wage salaries and benefits.”

Last week, D.C. Mayor Muriel E. Bowser (D) ushered waves of protesters into the street with a megaphone in hand.

She joined the group in a chant of “sí, se puede” and told them the District “cannot move forward without the people that help to make our office buildings work.”

Several of the workers who participated in Thursday’s march spend their days cleaning and maintaining buildings along the SEIU’s planned protest route: the World Bank, the International Monetary Fund and other businesses around International Square.

“These are very prestigious sites, and it just highlights how important the work that they do is,” said SEIU spokeswoman Julie Karant.

Bowser was joined last week by D.C. Council Chairman Phil Mendelson (D) and council member Elissa Silverman (I-At Large), who each took a turn addressing the crowd.

Organizers said the city leaders’ presence sends a message to the workers — and employers — that the District values the workers and stands behind their pursuit of strong labor protections, better hours and wages of at least $15 an hour.

In Loudoun County, janitors are bargaining for their first labor contract. Negotiations with the Washington Service Contractors Association began Sept. 15.

“We are only a few days away from the contract’s expiration, and we are still far” from reaching an agreement, Karant said. “Nobody wants to go on strike, but they are certainly willing to do whatever it takes to support their families.”

The demonstration was the fourth in about three weeks to converge on D.C. streets during rush hour. The first two protests, in September, involved activists who rallied in support of action to tackle climate change.

D.C. police did not issue a permit for the protest, but Karant said police had assured SEIU organizers that officers would be on site to secure the march.