The visit was approved in August by the Permanent Council of the OAS, handing the officials a brief "to carry out diplomatic efforts at the highest level to seek a peaceful and effective solution to the crisis in Nicaragua."
However, the OAS said in a statement the delegation had been informed by Nicaragua’s migration authorities that it would not be allowed into the country. President Daniel Ortega has previously described the mission an attempt to interfere in the internal affairs of his nation.
Jailed student leader Nahiroby Olivas told The Associated Press that an OAS secretariat notified him that the trip was being cancelled "because the government would not allow [officials] to enter the country."
Olivas is a member of an opposition coalition and was set to meet with commission representatives following their expected arrival on Monday.
Unrest began in Nicaragua in April 2018 after protests over changes to social security broadened to demand President Ortega's exit from office. The Inter-American Commission on Human Rights found that more than 325 people were subsequently killed in a government crackdown on dissenters.