Private link on U.S.-Mexico border

A traveler is directed as she passes through U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge between San Diego and the Tijuana airport on the facilities opening day in Otay Mesa, California December 9, 2015. The privately run facility allows ticketed passengers to skip long border waits and clear U.S. Customs for a fee. REUTERS/Mike Blake

Travelers walk along a bridge towards U.S. Customs and Immigration while using the Cross Border Xpress pedestrian bridge between San Diego and the Tijuana airport on the facility's opening day in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

A sign signifying the actual border line between the United States and Mexico is shown on the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

U.S. Customs and Immigration officers await travelers during the opening day of the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

A U.S. Customs and Immigration officer works a new border crossing during the opening day of the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

Travelers enter U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

A traveler arrives to pass through U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

A traveler passes through U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

U.S. Customs and Immigration officers await travelers in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

Travelers pass through U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge in Otay Mesa California December 9, 2015. REUTERS/Mike Blake

Travelers pass through U.S. Customs and Immigration after using the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

U.S. Customs and Immigration officers await travelers in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

A sign signifying the actual border line between the United States and Mexico is shown on the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

Traveler leaves the United States for Mexico as they use the Cross Border Xpress pedestrian bridge in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake

The Cross Border Xpress pedestrian bridge between San Diego and the Tijuana airport is shown on the facility's opening day in Otay Mesa, California December 9, 2015. REUTERS/Mike Blake