U.S. Rep. Maurice Hinchey, an upstate New York Democrat in his 10th term, plans to announce that he won't seek re-election.

The 73-year-old representative, who recently completed treatment for colon cancer, will make an official retirement announcement Thursday in Kingston, his office said Wednesday.

Hinchey, a senior member of the House Appropriations Committee, has been declared cancer-free by his doctors, his office said.

The 22nd Congressional District includes a large swath of upstate New York, from the Hudson Valley west to Binghamton and Ithaca. Hinchey received 51 percent of the vote in 2010 against Republican challenger George K. Phillips, who has established a website soliciting contributions for another congressional run.

New York will lose two of its 29 congressional seats under redistricting because other states grew faster in population. Democrats who control the process, however, could carve up Hinchey's district, which might strengthen nearby Democrats.

Republicans are expected to lose the other of the two seats.

There was no immediate comment Wednesday from New York State Republican Party Chairman Ed Cox.

Hinchey had previously served in the state Assembly, where he developed an expertise on environmental issues. He has been a vocal opponent of hydraulic fracturing for natural gas, a drilling technology that could be used in many areas of his district if allowed by regulators. Opponents say it threatens wells and aquifers.

Hinchey is the son of a cement plant worker who served in the Navy and was a toll collector for the New York Thruway. He lives in Hurley. He is married and has three children.