MEXICO CITY (Reuters) - The fourth round of talks to renegotiate the North American Free Trade agreement have been prolonged until Oct. 17, two sources in Mexico said on Tuesday, as negotiators gathering in Washington were expected to start tackling difficult issues. The round of talks due to begin on Wednesday is expected to include discussions about including quotas for U.S. content in autos, a major bone of contention for Mexico, Canada and many companies. Previously, the talks were due to end on Oct. 15. The news was first reported by Bloomberg earlier on Tuesday. 
NAFTA negotiation round extended by two days: Mexico sources