Before Cambodia, Kerry was in Laos, where he met with Lao Deputy Prime Minister and Foreign Minister Thongloun Sisoulith in capital Vientiane.
During the meeting, the two sides discussed a slew of issues from bombs and mines left over from war, health care, education, to drug crime prevention, environment, economy and trade.
Preparations for the ASEAN-U.S. summit were also on the agenda.
Laos is taking over as Chair of ASEAN in 2016, the first year of the ASEAN Community.
Kerry will leave Cambodia later Tuesday for China, the last leg of his three-nation Asian tour.