Jose Pimentel, a 27-year-old New Yorker arrested on charges of plotting to attack U.S. military personnel, police cars and post offices with homemade pipe bombs in the metro area, is an al-Qaida sympathizer, authorities say.

Pimentel was arrested Saturday in his apartment in Washington Heights, northern Manhattan. Police Commissioner Raymond W. Kelly, who appeared alongside Mayor Michael R. Bloomberg and Manhattan District Attorney Cyrus R. Vance Jr. at a Sunday night news conference, said Pimentel had begun to plot a bomb attack in August.

The suspect was a so-called lone wolf motivated by his own resentment of the presence of American troops in Iraq and Afghanistan as well as inspired by al-Qaida propaganda, Bloomberg said. 

Kelly said Pimentel, a convert to Islam also known as Muhammad Yusuf, had been under police surveillance for more than two years. He intended to test his plot by blowing up mailboxes before embarking on a bombing campaign around New York City, Kelly said.

He said Pimentel learned how to fashion a pipe bomb from instructions in al-Qaida's online propaganda magazine, Inspire, which is written in English.

Pimentel may have been motivated to carry out acts of terror by the killing of Anwar al-Awlaki, the leader of al-Qaida in Yemen, by U.S. forces on Sept. 30. Pimentel allegedly purchased some of his bomb-making supplies at a 99 cent store and at a Home Depot in the Bronx. On his Web site, Pimentel spoke of every Muslim's duty to wage war against the west, Vance said.