Simpson Thacher & Bartlett and Weil Gotshal & Manges have emerged as leaders in the US’ surging deal markets as new research shows that the value of US M&A this year is close to topping $1trn (£562bn).

The research by Thomson Financial shows the value of US M&A in the first three-quarters of 2005 is up 37% on the same period in 2004, hitting $987bn (£555bn).