PORTLAND, Ore. (AP) — Mayors from six U.S. cities with legal marijuana have formed a coalition with the aim of preparing other states and the federal government for legalization.

Mayors from Denver, Seattle, Portland, San Francisco, Los Angeles, Las Vegas and West Sacramento announced Monday on Twitter that they sponsored a resolution at the Conference of Mayors in Boston asking the U.S. government to remove cannabis from a list of illegal drugs, among other things.

Mayors from Oakland, California and Thornton, Colorado also pledged to actively advocate for federal reform of marijuana policy.

President Donald Trump said last week he would "probably" back a bipartisan congressional effort to ease a U.S. ban on the drug that about 30 states have legalized in some form. The bill supported by both parties was introduced June 7.