NUEVO LAREDO, Mexico (Reuters) - Glafiro Montemayor’s scrubland near the U.S. border may not look like much but within a few years he hopes to transform it by building a giant new bridge across the Rio Grande, setting his sights on billions of dollars in U.S.-Mexico trade. Hailing from a long line of Mexican customs brokers, Montemayor bristles at U.S. Republican candidate Donald Trump’s promise to build a wall between the two countries and his threat to rip up the North American Free Trade Agreement (NAFTA), a treaty that has been good to Nuevo Laredo. Montemayor believes Nuevo Laredo’s border bridges are near capacity and he wants to build another on his wiry, mesquite-filled land that could eventually develop into a bi-national free trade zone, luring investment and jobs. “He (Trump) wants to build walls, and the bilateral relationship requires that we build bridges,” Montemayor said in his air-conditioned office, surrounded by hunting trophies. Like Montemayor, many in trade-dependent Nuevo Laredo fear Trump’s proposed policies could threaten the city’s economic future and they hope Democratic candidate Hillary Clinton wins the Nov. 8 election. Nonetheless, some fear Clinton, who was first lady when her husband Bill signed NAFTA in 1993, may have absorbed some of the anti-trade views espoused by Trump and her Democratic primary campaign rival Bernie Sanders during a bruising campaign.  In particular, they fret about her public backtracking over the proposed Trans-Pacific Partnership, which is seen as a key driver of future growth for the city.      Trump calls NAFTA the worst trade deal ever signed by the United States, claiming Mexico got all the benefits and it led to U.S. firms shipping jobs south. He has vowed to renegotiate the treaty, or possibly even scrap it.  Over $1.5 billion in trade crosses the U.S.-Mexico border each day and few places rely as heavily on that commerce as Nuevo Laredo, a feisty northeastern Mexican border city full of factory workers and truckers, but also drug traffickers.  Every day, a 6-km (3.7-mile) line of trucks backs up into Mexico, waiting to haul everything from tomatoes to fridge freezers across the World Trade Bridge into Texas. Car parts, agricultural products and plastics go the other way.  At least 40 percent of bilateral commerce flows across that bridge and nearly 20 percent of Mexico’s value-added tax, or about $5 billion, is collected from the 12,500 trucks that cross the frontier each day, the World Trade Bridge authority says.  The bridge, it adds, is now the second most lucrative U.S. port after the Port of Long Beach in Los Angeles. On a visit to the bridge itself, it is easy to understand why Mexican drug cartels have fought vicious battles to control the Nuevo Laredo crossing, turning the city into a hotbed of teenage gunslingers and nervy soldiers.  Of the 6,500-odd trucks that enter the United States each day, officials can only search 1,000 at most. Drugs move north into the United States and guns and cash easily flow south. Bootlegging has long been a way of life here. The former Zetas cartel kingpin Miguel Trevino, aka Z-40, was born in Nuevo Laredo, and Edgar Valdez, or La Barbie, a one-time associate of jailed capo Joaquin “El Chapo” Guzman, is a native of Laredo, just across the river in Texas.   Those involved in legitimate cross-border trade clam up when talk turns to drug smuggling, a scourge that Trump has used to bash Mexico, and prefer to talk about lawful commerce. Since the September 11 attacks in 2001, when the United States tightened its borders, Nuevo Laredo’s business community learned the hard way that security was the primary concern for its northern neighbor. “Those days were terrible. The borders were almost closed,” said Carlos Martinez, a customs broker, radio host and academic. But as a result of U.S. security concerns, he said trade practices improved, with the development of efficient programs like the Free and Secure Trade (FAST) scheme which allows  trusted importers to transit quickly across the border. Ever since, the trend along the border has been for greater integration and more streamlined borders, Martinez said. For example, as of 2015, the Cross Border Xpress bridge allows travelers to cross seamlessly between Tijuana airport and San Diego. That same year, the first new rail bridge between Mexico and the United States in over a century opened.  So, regardless of campaign politics, some here believe Clinton is more committed to free trade than she has shown publicly in this campaign and that even Trump will need to protect bilateral trade if he wins. Sean Doherty, a 35-year U.S. Customs and Border Protection veteran, was involved in the development of the Customs-Trade Partnership Against Terrorism (C-TPAT), a supply chain program with over 11,000 companies enrolled that helps expedite secure cross-border commerce.  He said the program is one of many border schemes that both the U.S. government and thousands of businesses had invested heavily in to create and run.  “I think (Trump) would have a lot of push-back or blowback if he tried to disband that type of a program,” Doherty said.  “A lot of his rhetoric is just that, rhetoric. And if he does happen to win, I think a lot of things that he’s proposing - he’ll come back down to earth.” Miguel Conchas, president of the Laredo Chamber of Commerce, is also dubious Trump could fulfill all his campaign promises. Nonetheless, he said the Trump effect is already being felt across the river in Texas. The real estate mogul’s ascent has helped push the peso currency to record lows, hurting Laredo’s retail and banking businesses which rely on Mexican customers.  Alfredo Espinoza, who runs the World Trade Bridge trust in Nuevo Laredo, is downcast about the election, and feels a more protectionist era is imminent.  “We don’t think Trump is going to win,” he said, speaking in his office overlooking a seemingly endless line of trucks. “Nonetheless, Hillary ... won’t open the U.S. market, she will protect it. That scares us here in Mexico.” 