At the beginning of 1961, while the armed clashes continued, the Cambodian head of state N. Sihanouk proposed to convene an international conference of 14 powers to solve the Lao problem, characterized by the existence of two opposing governments recognized and supported by the opposing blocs, and made more complex by neutral support for a third government headed by Souvanna Phouma. The Cambodian initiative was opposed by Westerners, while the London government proposed to revive the Indo-Polish-Canadian control commission. After difficult negotiations conducted mainly in London and Moscow, on April 24 the parties were asked to cease fire, the neutral commission was restored and an international conference was convened on the basis of the proposals formulated by Sihanouk.
According to indexdotcom, the conference, which met in Geneva on May 16, immediately ran aground in the face of the conflict on basic issues between the United States and China. The situation was unblocked by an agreement reached on June 22 in Zurich, on the margins of the conference, between the three Laotian princes. It provided for the formation of a single government, the integration of the various armies, the neutralization of the kingdom. After some resistance opposed by Phoumi Nosavan and Boun Oum and overcome by the pressure of the United States to suspend economic aid, the three parties agreed on the constitution of a provisional government of national unity chaired by Souvanna Phouma, and on 23 July 1962 a document to this effect it was signed in Geneva. However, the prospects for pacification were once again frustrated by reactions from the right. In fact, on April 10, 1963, the foreign minister, the neutralist Quinim Pholsena, was assassinated and the political exponents of the left were forced to leave Vientiane. On April 19, 1964, a group of generals, opposed to the moderate line of Phoumi Nosavan and supported by the Americans, seized power. Souvanna Phouma, abandoning the neutralist position, adhered to the formation of a strong government and the merger between the forces of the right and the neutralist ones. This provoked the immediate reaction of the Pathet Lao, which resumed the fighting and occupied the entire Plain of Jars, of vital strategic importance. To overcome the impasse, a new Interlaotian tripartite conference was convened in August in Celle-St-Cloud; but on November 21, after an agreement on the agenda had been painstakingly reached, Souvanna Phouma left the works. In 1965 the escalation American air struck the Laos; but the Pathet Lao, with the support of the former left neutralists headed by Kong Lê, continued its military expansion towards the south, consolidating the areas under its control. In August 1970 the guerrillas surrounded the royal capital of Luang Prabang and Souvanna Phouma agreed to enter into negotiations; but on February 8, 1971, troops from Saigon, with American air cover, entered the Laos in force to interrupt the Ho Chi Minh runway and destroy the North Vietnamese bases. The operation totally failed. The forces of the Pathet Lao, despite the American bombings (in total more than 2.5 million tons of bombs, equal to 130 atom bombs in Hiroshima) resumed the initiative, they reoccupied the Plain of Jars they had lost and forced the Americans to abandon the secret bases of Lon Chen and Ban Yu. The government of Vientiane was forced to accept the offer repeatedly repeated by the Pathet Lao to enter into negotiations and on February 21, 1973 a protocol was signed in Vientiane that put an end to the hostilities, providing for the withdrawal of foreign soldiers (Thais, North Vietnamese and advisors Americans) within 60 days and envisaged a political solution based on a coalition government and a National Political Council with the equal participation of the right-wing elements and the former neutralists of Souvanna Phouma on the one hand, of the Neo Lao Haksat, that is of the front of the left led by the Pathet Lao on the other. On April 5, 1974, the national unity government headed by Souvanna Phouma was installed, while the head of the Pathet Lao, Prince Souphanouvong, assumed the presidency of the National Council.