Mexico has defended the release of a set of stamps showing a popular black cartoon character, following strong criticism from the US.
US campaigners want the stamps withdrawn
The White House spokesman said racial stereotypes had no place in the modern world, and civil rights leader Jesse Jackson called the stamps "an insult".
Mexico said Mr Jackson was uninformed about Mexican culture and Memin Pinguin had in fact done a lot to fight racism.
It is the second time in a month that Mr Jackson has clashed with Mexico.
In May President Vicente Fox apologised for saying Mexican migrants in the US did jobs "even blacks don't want".
He said the comment was taken out of context, which had been made to express frustration with tough new immigration legislation approved by the US Senate.
'Like Speedy Gonzalez'
The latest row comes after the Mexican government issued a series of five stamps of Memin Pinguin.
The cartoon character from a comic book created in the 1940s has exaggerated eyes and lips.
Mr Jackson said President Bush should pressure Mexico to withdraw the stamps from the market.
"It is offensive," he said.
The National Association for the Advancement of Coloured People (NAACP) called the stamps "injurious to black people who live in the United States and Mexico."
Correspondents say there are currently no plans to withdraw the 750,000 commemorative stamps set for release.
A spokesman for Mexico's president on Thursday noted that the cartoon had in the past helped to promote family values, and called the adverse reaction "strange."
One Mexican diplomat responded that the character was no more offensive than the cartoon Mexican mouse, Speedy Gonzalez.