NEW YORK -- The head of the nation's oldest civil rights organization on Saturday urged readers to boycott the New York Post, calling a cartoon the tabloid published an invitation to assassinate the president.

Earlier this week, the newspaper apologized to anyone who might have been offended by the image, which some say likens President Barack Obama to a violent chimpanzee gunned down by police in Connecticut.

But the apology wasn't good enough for the NAACP, and President Benjamin Todd Jealous said the cartoon printed Wednesday was "an invitation to assassination."

He said the tabloid should remove editor-in-chief Col Allan, as well as longtime cartoonist Sean Delonas.

On Thursday, after a series of protests by notable figures including director Spike Lee, the paper posted an editorial on its Web site saying the cartoon was meant to mock the federal economic stimulus bill, but "to those who were offended by the image, we apologize."

A spokeswoman for the newspaper Saturday referred The Associated Press to the paper's editorial when asked about the proposed NAACP boycott.

Jealous called the editorial "a half of an apology, without elaboration." The drawing, he said, "picks off the scabs of all the racial wounds."

He spoke as the National Association for the Advancement of Colored People gathered for its annual meeting in New York, where it was founded a century ago.

Jealous was joined by NAACP officials, including Chairman Julian Bond and Myrlie Evers-Williams, widow of slain civil rights leader Medgar Evers, who was honored with one of six new U.S. postage stamps officially unveiled Saturday. They commemorate the lifelong achievements of NAACP founders and leaders.

In addition to electing new board members, the NAACP is marking the centennial of the grass-roots organization that is still seeking reparations for slavery.

The NAACP officials said that if the Post does not take "serious disciplinary action," they would reach out to organizations across the country to join them in their efforts against the tabloid.

Bond called publication of the cartoon "thoughtlessness taken to the extreme. ... Anyone who is not offended by it does not have any sensitivity."