Austin, Texas - The United States and Mexico on Tuesday opened their first new rail link in more than a century as part of plans to update infrastructure carrying nearly $600 billion a year in bilateral trade, officials said.

The West Rail Bypass International Bridge connecting Brownsville, Texas with the city of Matamoros across the border will largely carry freight, the US Commerce Department said.

Since the North American Free Trade Agreement was implemented over 20 years ago, trade with Mexico has increased six-fold and Mexico has become one of the biggest trading partners with the United States, US Secretary of Commerce Penny Pritzker said. "But the infrastructure has not improved," she told Reuters by telephone.

"We need to have infrastructure that lives up to the economic opportunities that are in front of both of our countries," she said, adding the two governments have launched other projects aimed at making trade easier.

The West Rail project broke ground in December 2010 and was designed to expand regional transportation capacity, improve air quality and alleviate urban congestion by re-routing rail traffic out of the most populated areas in both border cities, the Commerce Department said.

The new crossing comes as prominent American politicians, mostly Republicans, have called for tightening controls along the border to prevent illicit goods from crossing and immigrants from entering the United States illegally.

Before the new bridge opened, there were eight rail crossings between the United States and Mexico, according to US Customs and Border Protection. All the locations are equipped with X-ray systems that can scan arriving rail traffic. There are also Border Patrol agents and sniffer dogs for on-site inspections, it said.

Mexico is the third-largest bilateral goods trading partner of the United States and the United States’ second-largest goods export market in 2013, according to the Office of the US Trade Representative.

US-Mexico trade increased to $592 billion in 2014 with nearly $1.5 billion of goods crossing between the two countries each day, the Commerce Department said.