U.K. stocks fell Monday, with lower oil prices and a ratings downgrade from J.P. Morgan weighing on investor sentiment. Meanwhile, the Confederation of British Industry said Monday that U.K. exports over the last quarter grew 8%, logging its highest balance since April 2014, aided by weakness in the pound, which has been slammed in the wake of the Brexit vote in June.

U.S. stocks pulled back from session highs but ended with gains Monday, getting a lift from a heavy round of merger announcements, including AT&T's planned acquisition of Time Warner. The tech, consumer-discretionary and consumer-staples sectors led the gains, while telecoms and energy sold off. Earlier, the index had been up nearly 14 points.

Japanese shares hit a six-month top on Tuesday as the dollar advanced on the yen, while risk sentiment got a lift after factory surveys in the United States and Europe boasted the best readings of the year so far.