U.S. Rep. Jim McDermott, D-Wash., speaks at a pro-refugee protest organized by Americans for Refugees and Immigrants in Seattle, Nov. 28, 2015. Reuters / Jason Redmong

Democratic Rep. Jim McDermott, in his 14th term representing Seattle, is set to announce his retirement, the Associated Press reported Monday. The 79-year-old congressman from Washington state has been calling colleagues to inform them of the decision, a Democratic Party official told the AP.

The official spoke to the news service on the condition of anonymity ahead of a scheduled Monday news conference for McDermott. The news conference is expected to include an "important" announcement, reported KING 5 in Seattle. McDermott's camp has not confirmed the retirement reports, but sources "with longtime experience in Democratic Party politics" told KING 5 that McDermott will announce Monday he is not running again.

McDermott, a psychiatrist who served in the Navy, has been known as an outspoken liberal in Congress, representing a district that includes much of Seattle and is known for leaning strongly toward the left. McDermott has made inequality issues and health care reform top priorities throughout his career. He was elected in 1988, and had been dubbed Seattle's "congressman for life," according to the Seattle Post-Intelligencer.

McDermott drew attention in 2004 for leaving out the phrase "under God" while leading the Pledge of Allegiance in the House, later saying it was an unintentional omission. (The words were not in the original pledge and were added in the 1950s.) McDermott has often clashed with Republicans. Most notably, he was involved in a legal battle with former Speaker John Boehner, R-Ohio, after leaking to the media an illegally recorded phone call between Boehner and other GOP leaders. McDermott ultimately had to pay Boehner more than $1 million in damages.

McDermott won his last re-election with nearly 80 percent of the vote and his district is assumed to remain under Democratic control in the 2016 elections, the Hill reported. It has not elected a Republican congressman since 1977, and President Barack Obama carried it with 79 percent of the vote in 2012.

Democratic state Rep. Brady Walkinshaw announced last month he planned to challenge McDermott in the district. Walkinshaw, also an outspoken liberal, will now reportedly no longer have to face the longtime congressman.