Guatemalan conservative Alejandro Giammattei secured a crushing victory in a presidential election Sunday, and promised to seek better terms for his country from an unpopular migration deal agreed with Washington under duress last month.

With preliminary results from over 99 percent of polling stations counted, the electoral tribunal declared Giammattei the winner with more than 58 percent of the vote, ahead of his center-left rival, former first lady Sandra Torres, with 42 percent.

Speaking a few hours before being declared the winner, Giammattei said he wanted to see what can be done to improve the deal that outgoing President Jimmy Morales made to stem U.S.-bound migration from Central America.