The arrests, which took place late Wednesday in the Riverdale section of the Bronx, were made after the men were said to have placed FBI-altered bombs outside a synagogue and Jewish community center. The police, using an 18-wheel truck, blocked their getaway and then apprehended the unarmed suspects.
According to news reports, New York City police commissioner Raymond Kelly, at a news conference, quoted one of the men as saying, "If Jews were killed in this attack ... that would be all right." A federal complaint states that one of the alleged conspirators said he wanted to do "something to America."
Separately, President Obama, in a major speech Thursday morning on terrorism and Guantánamo, said his most important responsibility as president is to keep the American people safe. "That is the first thing that I think about when I wake up in the morning. It is the last thing that I think about when I go to sleep at night," he said at the National Archives in Washington.
"We know that Al Qaeda is actively planning to attack us again. We know that this threat will be with us for a long time and that we must use all elements of our power to defeat it," Mr. Obama said.
The FBI apparently was aware of this latest plot for some time, because of the work of a confidential informant. The bureau says it monitored the suspects' actions with wiretaps and video cameras in their homes and provided an inactive missile and inert explosives. At least eight law-enforcement agencies were involved in the case.
The government filed a sealed complaint a day before the arrests.
According to the federal complaint, the four men selected their targets in April and conducted surveillance, including taking photos, of military planes at the Air National Guard base at Stewart Airport in Newburgh, N.Y. The government says that all four men live in Newburgh, a Hudson River community in Orange County.
The four who are charged are James Cromitie, David Williams, Onta Williams, and Laguerre Payen. According to news reports, quoting US officials, three of the men are US citizens, and one is of Haitian descent. The Associated Press says three are converts to Islam.
The American-Arab Anti-Discrimination Committee, the largest Arab-American civil rights organization, issued a statement Thursday condemning the purported effort. "This alleged act of hate is absolutely unacceptable," said Kareem Shora, ADC's national executive director, in a statement. The ADC also said that hate-motivated violence is not associated with nor representative of any specific race, religion, or ethnicity.
The plot is alleged to have begun last June, when Mr. Cromitie told an FBI informant that he was upset over the killing of Muslims in Pakistan and the war in Afghanistan, where he said his parents had lived. He told the informant if he were to die a martyr, he would go to "paradise," according to the complaint. The informant told Cromitie he had links to Pakistan-based Jaish-e-Mohammed, which is designated a terrorist organization by the US government.
In late April, Cromitie and David Williams are alleged to have purchased a 9-millimeter semiautomatic pistol for use during the planned attacks. Then, in early May, the complaint says, Cromitie, David Williams, and Mr. Payen drove with the informant toward Stamford, Conn., to obtain what they thought would be a surface-to-air guided missile and three improvised explosive devices containing 30 pounds of C-4 plastic explosives. Both had been neutralized by the FBI.
According to the complaint, the informant told the men he had obtained the material from Jaish-e-Mohammed.
"While the weapons provided to the defendants by the cooperating witness were fake, the defendants thought they were absolutely real," said Acting US Attorney Lev Dassin in a statement.
The men are now charged with conspiracy to use weapons of mass destruction and conspiracy to acquire and use antiaircraft missiles. The maximum penalty for both charges is life in prison.
• News wires were used in this story.