Peabody Energy ( BTU) agreed to buy Australia's Excel Coal in a deal that values the target company's stock at $1.34 billion.According to the takeover plan, Peabody will pay $6.21 in cash for each share of Excel. Peabody will also assume around $190 millon of debt. Peabody is the world's largest private-sector coal company, and Excel is one of the biggest independent coal companies in Australia. Peabody said the acquisition should add to its earnings starting in 2007. Last year, Peabody sold 240 million tons of coal and had $4.6 billion in revenue. Excel produced about 5.6 million tons of coal in calendar-year 2005, but that should grow to as much as 15 million tons next year. Peabody's shares fell $1.41, or 2.5%, to $54.92 in regular trading. The stock regained 8 cents to $55 in after-hours trading.