Sept 27 (Reuters) -
* Mexican economy minister says third round of NAFTA negotiations was "highly productive"
* Mexican economy minister says encountered differences in some issues in NAFTA talks, will have substantial challenges in next round
* Canadian Foreign Minister Freeland says negotiations completed on chapter on small and medium-sized enterprises
* Canadian Foreign Minister Freeland says meaningful advances made in telecoms, customs and trade facilitation
* Canadian Foreign Minister Freeland says negotiators working from consolidated texts in most areas
* Canadian Foreign Minister Freeland, in reference to NAFTA talks, says "we never said this was going to be easy"
* NAFTA negotiators says next round of talks will be in Washington from oct 11-15
* NAFTA negotiators say expect to conclude the negotiation on competition chapter before the next round Source text for Eikon: Further company coverage: 1/8 3/8 (Reporting by David Ljunggren)