With a spot in the 2014 Copa Sudamericana first stage on the line, the two teams will play for a place in the continental competition.
Jose Cantillana's Cobresal edged to a 3-2 win at Universidad Concepcion to win by the same score on aggregate, while Palestino's 4-0 thrashing of Cobreloa completed a 5-0 victory.
Juan Cabral put Concepcion ahead on 17 minutes, but a Hans Salinas penalty soon after saw Cobresal level.
Alvaro Navarro added another and while Pedro Munoz equalised, Ever Cantero struck again for Cobresal to complete their win.
Palestino were comfortable at home to Cobreloa.
Juan Duma doubled their aggregate lead in the 38th minute before he struck in the second half to go with goals from Renato Ramos and Sergio Lopez.
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