Denver Mayor Mike Johnston is heading to Washington, D.C., as the head of a coalition of mayors asking for help with the migrant crisis.

Johnston, a Democrat, will use the United States Mayors Conference to advocate federal assistance in dealing with the migrant crisis. Denver is one of several Democratic-controlled cities that have been the target of Gov. Greg Abbott’s (R-TX) migrant busing campaign, which has seen Texas ship thousands of immigrants to the sanctuary cities.

“In D.C. this week for the @usmayors conference to work with fellow mayors, our federal delegation and the White House to advocate for federal action on the migrant crisis,” Johnston said in a post on X, formerly Twitter.

Johnston has previously sounded the alarm on his city’s inability to accommodate the influx of immigrants. On Sunday, he told Fox News that the current influx was “unsustainable.”

“It is unsustainable,” Johnston said on Fox News Sunday. “In the current structure, when we have 30 or 40,000 people arriving without work authorization, without federal support, it is going to be a huge strain on cities.”