Giammattei added that he would meet with President-elect Bernardo Arevalo, who was swept to victory vowing to tackle corruption, on September 4.
"The doors are now open towards an orderly, transparent, and above all, efficient government transition," said Giammattei, speaking in a video message published online.
Giammattei's statement came after a document from the citizens registry ordering a temporary suspension of Arevalo's Semilla party's legal registration caused new confusion over the election results.
Arevalo, a 64-year-old ex-diplomat and son of a former president, won the Aug. 20 second-round run-off with more than 58% of the vote after prosecutors had earlier threatened to bar Semilla, from the election, prompting international outcry.
On Monday, the country's electoral tribunal officially declared Arevalo the victor at a press conference, but faced questions about the new suspension attempt.
Arevalo has said the suspension is illegal.
The Organization of American States (OAS), which observed the country's electoral process and called the suspension attempt unjustified, would also be present until Arevalo is due to take office on Jan. 14, Giammattei said.
(Reporting by Sofia Menchu, Writing by Isabel Woodford; Editing by Cassandra Garrison)
