WASHINGTON: President Barack Obama named US ambassadors to Japan, India and Sri Lanka, amid heightened tension in Asia over North Korea's nuclear tests, unrest in Pakistan and ethnic tension in Sri Lanka.

Obama tapped to longtime Internet and biotechnology lawyer John Roos as his ambassador to Japan, and turned to former Democratic congressman Timothy Roemer to be his eyes in India, the White House said.

Roos, who served as the Northern California finance chair for Obama's 2008 presidential campaign, is chief executive officer of a law firm in Palo Alto, California.

Recent US ambassadors to Tokyo have included former vice president Walter Mondale and former senior lawmakers Howard Baker and Mike Mansfield.

During his tenure at Wilson, Sonsini, Goodrich & Rosati, Roos "helped lead the firm during the various waves of innovation in Silicon Valley," the White House said in a statement.

Roemer served on the blue-ribbon commission investigating the September 11, 2001 attacks on New York and Washington, and on a key committee to prevent nuclear proliferation. He represented a district from the midwestern state of Indiana from 1991 to 2003.

Obama picked Patricia Butenis, a career diplomat who has previously been posted in Baghdad, Pakistan and New Delhi, as his ambassador to Sri Lanka and the Maldives.

The ambassadors will "strengthen our partnerships abroad at this critical time for our nation and the world," Obama said in the statement.

All of the ambassador nominations require US Senate confirmation.