Mayor Bill de Blasio and his counterparts in other cities sent a letter to congress Thursday urging it to oppose legislation that would withhold federal funds to "sanctuary cities."

Both the House and Senate are mulling bills that would affect those municipalities that have laws that protect undocumented immigrants from direct investigations by the Department of Immigration Services.

Although the bills came in light following the July 1 murder of Kathryn Steinle in San Francisco, Cities United for Immigration Action, a coalition of 21 mayors, said "overbroad immigration enforcement undermines safety for all."

"At this time of mourning, we urge our members of Congress to refrain from politicizing this tragedy and fueling an anti-immigrant sentiment," the coalition wrote in its letter to the leaders for both governing bodies.

Steinle, 32, was allegedly killed by Juan Francisco Lopez-Sanchez, an undocumented immigrant, while walking with her father. Lopez-Sanchez wasn't prosecuted for a drug offense earlier in the year even though federal immigration officers put out an order to have him in custody.

President Barack Obama indicated he would veto any law that would cut the funding to the sanctuary cities.