President Barack Obama is asking Congress to formally authorize war against Islamic State militants and says the group could threaten the U.S. homeland if left unchecked.

The president is sending Congress a proposed three-page resolution on Wednesday to authorize military force. In a letter to lawmakers accompanying the request, Obama urges them to "show the world we are united in our resolve to counter the threat."

Obama's resolution and letter were provided to The Associated Press. He plans to speak on his request from the White House Wednesday afternoon.

Obama would limit authorization to three years, with no restriction where U.S. forces could pursue the threat. Obama's proposal bans "enduring offensive combat operations," an ambiguous term intended as compromise between lawmakers who want authority for ground troops and those who don't.