Western New Guinea had been part of the Dutch East Indies, and Indonesian nationalists had thus claimed it on this basis. Indonesia was able to instigate a diplomatic and military confrontation with the Dutch over the territory following an Indonesian-Soviet arms agreement in 1960. It was, however, United States pressure on the Netherlands that led to an Indonesian takeover in 1963. Also in 1963, Indonesia commenced "Konfrontasi" with the new state of Malaysia. The northern states of Borneo, formerly British Sarawak and Sabah, had wavered in joining Malaysia, whilst Indonesia saw itself as the rightful ruler of Austronesian peoples and supported an unsuccessful revolution attempt in Brunei. Reviving the glories of the Indonesian National Revolution, Sukarno increased the anti-British sentiment in his rhetoric and mounted military offensives along the Indonesia-Malaysia border in Borneo. As the PKI rallied in Jakarta streets in support, the West became increasingly alarmed at Indonesian foreign policy and the United States withdrew its aid to Indonesia.