Sanchez, 23, trained with United for two weeks at training camp in Florida. He is a right-sided player and will provide back-up for probable starter Nick DeLeon.
Sanchez is awaiting visa approval in order to become eligible for regular season matches. United opens the 2013 campaign Saturday night at Houston.
Sanchez, who had an assist in the preseason finale Saturday, is a regular with Panama’s national team and will report to camp in a few weeks ahead of World Cup qualifiers at Jamaica on March 22 and against Honduras at home four days later.