 Complete the following phrase:  The period between 1960 and 1968 also marked a cold period in the political relations between Sweden and the U.S., mainly due to the Swedish governments vocal opposition to the Vietnam War. In February 1968, the US recalled its Ambassador from Sweden after the Swedish Minister of Education and future prime minister Olof Palme, a Social Democrat, had participated in a protest in Stockholm against the war together with the North Vietnamese Ambassador to the Soviet Union Nguyen Tho Chan. The post of US Ambassador to Sweden remained vacant until February 1970. In December 1972, Olof Palme then Prime Minister made a speech on Swedish national radio where he compared the ongoing 