Thanks to higher birth rates and immigration, the Latino population stood at 37 million, compared with 36.2 million for black Americans, according to the US census bureau. Between 2000 and 2001 the number of Hispanics in the US grew by 4.7% and now comprises 13% of the population, compared, to a rise of 1.5% among black and African-Americans, who total 12.7%.

"It is a turning point in the nation's history, a symbolic benchmark," Roberto Suro, director of the Pew Hispanic Centre, a Washington-based think-tank, said.

Demographers expect the gap to widen significantly in future, which could have widespread implications for the national debate about race, as well as the broader political scene. With the white population falling, it will force mainstream political parties to tailor their messages more closely to the needs of minority voters, and Hispanics in particular.

"It forces the country to really change the way it thinks about itself. If you see the world in white and black, you are not describing the United States," Mr Suro said.

"It's important to remember that there will be fewer Latino voters than African-Americans for some time, because many are young and many are not yet citizens. Nor are they a cohesive bloc that can be relied upon to vote for one particular party. But with every election cycle, you see more attention paid to Latino voters."

More than half of all Latinos are concentrated in California, Texas and New York state. Add their numbers to the black population and white people become the minority in California and New Mexico, and barely a majority in Texas. Between them these states account for more than a third of the electoral college votes needed to win the US presidency.

More than 80% of African-American voters backed the Democrats in the presidential election of 2000, while about two-thirds of Hispanics voted Democrat in last year's mid-term elections.

Whether this will make any difference will depend on the Hispanic community's ability to unite on specific issues of common concern, said Ron Walters, political science professor at the University of Maryland, The category includes everyone from wealthy Cubans in Florida, whose families may have been here for a generation or more, to impoverished recent immigrants from Mexico in Texas.

"Blacks are more culturally cohesive," he told the Washington Post. "Latinos are far more disunified, because they have many, many ethnic groups. They're going to have to mobilise around the issues of language and immigration to thrust them into the political mainstream. There's a question in my mind as to whether the Hispanic community can do that."

A larger allocation of scarce resources to minority communities will also hinge on whether African-Americans can find common cause with Hispanics.

Organisations representing both communities have been keen to play down the demographic turnaround.

"Rather than comparing groups we should be looking at the status of communities," said Sonia Perez, deputy vice president of the National Council of La Raza, a national organisation representing Hispanics in the US. "When you look at Latino and African-American communities, the agendas are not that different. We share many of the same issues, interests and values."

The poverty rates of black and Hispanic Americans in 2000 stood at 23 and 21% respectively, nearly three times the rate for whites, the census bureau reported.

"There are those who would like to pit the African-American community against the Latino community that share an awful lot more in common than we do in differences," said Hillary Shelton, director of the NAACP's Washington bureau. "They're trying to get racial groups to fight each other over a small sliver of a pie."