Democrat John Kerry swept primaries in four southern states getting an average of about 66 per cent votes.

Kerry won over 70 per cent votes in Florida and Mississippi, more than 64 per cent in Texas and around 70 per cent in Louisiana.

He had virtually wrapped up nomination in the last week's primaries, which led to the exit of John Edwards, the last serious candidate in the field.

Bush, who had virtually no challenger, wrapped up an almost non-existent race for the Republican presidential nomination winning more than needed delegates in the four southern states that held primary elections.

Addressing cheering supporters in Chicago after sweeping the nominating contests in the four states yesterday, Kerry criticised Bush over issues ranging from economy to health care, foreign policy, fight against terrorism and the war in Iraq.

"This president doesn't have a record to run on, he has a record to run away from," Kerry claimed. "That's why voters said change is coming to America. Let's send George Bush back to Texas and take back the White House."

Kerry also challenged Bush to a monthly debate ahead of the November vote. "If the president wants to have a debate a month on just one subject and we go around the country, that would be a great idea. Let's do it."

For the Vietnam hero, the major issue now is to select a running mate who would become Vice president in case he wins the White House. Serious discussions are on among the party's top leadership on the issue. 

Meanwhile, Bush accused Kerry of favouring economic isolation as a means to counter competition from abroad and the loss of American jobs.

"There are economic isolationists in our country who believe we should separate ourselves from the rest of the world by raising up barriers and closing off markets. They're wrong," Bush said at a ceremony in Virginia without naming Kerry.

"If we are to continue growing this economy and creating new jobs, America must remain confident and strong about our ability to trade in the world," he added.

Kerry countered the charge by saying that the loss of nearly three million jobs since Bush took over reflected the Republican's 'trial of broken promises'.