He was baptized on 26 August in the same year of his birth in the Church of San Lorenzo Intramuros by one of his mother's relatives, the priest Pedro de Mier y Terán.

These characteristics, added to his military performance, figured as a favorable antecedent in the recommendation for his election among the candidates for governor of Paraguay written by his superior: He has always had credit for higher instruction than the previous two [...] His 36 years of service are certain and he has contracted a distinguished merit of war in them.The candidate definitely had the conditions to carry out the Bourbonic ideal of militarizing the Indian civil administration in order to achieve order, prompt obedience and discipline.

Velasco did not hide his fear of governing due to his self-descriptive lack of knowledge as recorded in an expedient from c. 1804 cited by historian Ezequiel Abásolo:Such was the situation of [...] Velasco, who at the time of being proposed to direct the destinies of the Missions, he made present "that the office of a political government" imposed him "the greatest fear, lacking the knowledge to handle the affairs" with knack, "reason why in the case of being selected by the King, he would only remain with" the consolation that the mistakes or faults committed by him would be unintentional.Due to the ruinous state of the Guarani reductions after the expulsion of the Jesuits, the King Charles IV decided to create, by a Royal Decree on 28 March 1803, a military and political government of the called "thirty towns of the old Guarani Missions".

The Lieutenant colonel Velasco arrived in Buenos Aires in January 1804 and on 2 August, the viceroy Joaquín del Pino authorized the cost of the trip with soldiers, an adviser, servants and luggage that would join him.

[4] Taking into consideration the state of the militias and the Lusitan expansionism over the zone, he proposed himself the creation of a force of 600 well-armed and disciplined soldiers, but due to a series of factors this could not overcome the third part.

The Intendant Governor of Paraguay, Lázaro de Ribera y Espinoza, had become a tyrannical, venal official, lacking sincerity and respect for his superiors.

[6] Furthermore, since 1789, he was harshly opposed to the Viceroy of the Río de la Plata Marquis of Avilés on the complex abolition of the community system of the Guarani peoples and its possible consequences.

He ruled until the beginning of 1807, when he was called by the Viceroy of the Río de la Plata to help organize the army to resist the British invasions of the River Plate.