Barack Obama has accepted his Democratic Party's historic presidential nomination, and has embarked on a two-month campaign for the White House as the first African-American to lead a major party ticket.

Senator Obama and his running mate, fellow Senator Joe Biden, Friday travel to Pennsylvania on a bus tour of key battleground states.

Thursday night, Obama appeared before nearly 80-thousand cheering supporters, promising change and drawing sharp contrasts with his Republican rival, John McCain.

In a speech filled with policy specifics, Obama said McCain would simply continue what he described as the failed policies of  President George Bush.

Obama vowed to end the Iraq war responsibly and finish the fight against al-Qaida and the Taliban.  He vowed to cut taxes for working families, stop giving tax breaks for corporations that move jobs overseas, and end U.S. dependence on foreign oil.

McCain's campaign called the speech "misleading" and "so fundamentally at odds with the meager record" of Obama, a first-term U.S. senator.

Republicans hold their national convention next week in Minneapolis-St. Paul, Minnesota, where McCain will become that party's presidential nominee.