HARRISBURG -- Republican U.S. Rep. Lou Barletta of Pennsylvania, a crusader against illegal immigration, is telling GOP officials and activists that he's decided to run for the U.S. Senate seat now held by Democrat Bob Casey.

A person familiar with the discussions tells The Associated Press that Barletta began telling party officials of his decision last week. The person spoke on condition of anonymity Monday because Barletta has not yet made his plans public.

In a text message, Barletta said his conversations have been "very positive" and he will announce his decision in a few weeks.

The 61-year-old congressman is in his fourth term. As the former mayor of Hazelton, Pennsylvania, he tried to advance municipal laws targeting immigrants in the country illegally.

The 57-year-old Casey is seeking a third term next year. Barletta would become the most recognizable name among his challengers.