A rookie police officer, with only weeks on the job, crossed paths with the would-be terrorist who is charged with plotting to bomb the Herald Square subway station. Beginning in November 2002, the undercover officer made visits to an Islamic bookstore in Bay Ridge, Brooklyn, and said he listened to the store clerk, Shahawar Matin Siraj, 23, predict further attacks on New York City, possibly on Wall Street.

The officer, who testified yesterday at Mr. Siraj’s trial in Brooklyn federal court under a pseudonym, Kamil Pasha, retold of conversations that suggest that Mr. Siraj drew satisfaction from tragedies ranging from suicide bombings in Israel to the loss of the space shuttle Columbia.

This snapshot of Mr. Siraj contradicts what the defense has maintained since the trial began four weeks ago. His legal team has sought to show that Mr. Siraj transformed into a would-be subway bomber from a mild-mannered young man after 2003. Around that time, Mr. Siraj met an older man who was employed by the police department as a confidential informant. Mr. Siraj’s lawyers say the police informant pushed Mr. Siraj to hate America, entrapping him into plotting against the subway station at 34th Street. If convicted, Mr. Siraj faces a maximum of 20 years in prison.

Mr. Siraj, who was arrested in August 2004 along with another man, yesterday expressed some remorse for the bomb plot. He said: “Yes, I am really sorry for those things. I am ashamed of it.”

The prosecution disclosed on Tuesday that a police officer had evidence Mr. Siraj regularly spoke on the topics of terrorism and jihad more than a year before the defendant first met the informant in late 2003. Mr. Pasha testified that in late 2002 he was making reports from the Islamic bookstore. Earlier in the trial, the confidential informant gave testimony lasting eight days.

“I asked if there would be suicide bombings in the United States,” Mr. Pasha testified yesterday. “He said, ‘Yes, because of the United States’ support for Israel.”

The two men also spoke on February 2, 2003, one day after the space shuttle Columbia broke up.

“The American people got what they deserve,” Mr. Pasha recalled Mr. Siraj as saying.

In a letter to the judge, Nina Gershon of U.S. District Court in Brooklyn, a lawyer for Mr. Siraj, sought to preclude Mr. Pasha from testifying. The lawyer, Martin Stolar, said Mr. Pasha would testify that Mr. Siraj “holds unpopular political views and supports unpopular political figures” and not about any “predisposition to engage in a terrorist conspiracy.”