The average cost of a domestic trip?encompassing air, car and hotel - will increase 6 percent to $1,110, said Mike Streit, vice president and global leader for American Express Business Travel Global Advisory Services. An international trip is expected to see a sharper increase of $205, to an average of $3,171 per trip.

According to Amex, projected domestic economy class airfares are expected to rise between 1 percent and 5 percent and international business-class airfares between 5 percent and 10 percent in 2008. Europe is expected to see similar increases. Amex's projections are based on a blend of projected published and corporate fares from clients, said Mitch Cwanger, air practice leader for American Express Business Travel Global Advisory Services.

Amex forecasts moderate hotel rate increases in North America, including mid-range increases of 4 percent to 7 percent and upper-range hikes between 5 percent and 8 percent in 2008.

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