美国国防部长马蒂斯周三前往美国南部边境，那里已部署了数千名美军，以支援边防巡逻人员。
马蒂斯星期二在五角大楼对记者说，目前“美军任务”“没有改变”。
他说，“我们正在布置边界隔离障，我们在那里有直升机，”他说，“我们要看未来会怎样，但现在这是我唯一的任务。”
美国总统特朗普呼吁加强边境安全，以防止寻求庇护的中美洲移民大军进入美国，并为此数次宣布这种来美方式带来“国家紧急状态”。
应国土安全部的请求，现有5,600名军人和另外2,100名国民警卫队队员已进入美国边境地区。
一名美国国防官员告诉美国之音，马蒂斯将视察德克萨斯州的麦卡伦，那里部署了大约1000名美军。
美国法律禁止被派往边境提供安全保障的美国军队参与国内执法，例如逮捕过境的移民等。
Secretary of Defense Jim Mattis is due to visit the U.S. southern border Wednesday, where thousands of American troops have been deployed to support border patrol agents.
Speaking to reporters Tuesday at the Pentagon, Mattis said there has been “no change” to the U.S. military mission “at this time.”
"We're doing the obstacle emplacement, we do have helicopters down there,” he said. “We will have to see what the future holds, but right now that is the only mission I have.”
President Donald Trump called for increased border security to prevent a caravan of asylum-seeking migrants from Central America from entering the United States, declaring on several occasions its approach constituted a "national emergency."
More than 5,600 active duty troops and another 2,100 National Guard troops have moved into the U.S.-Mexico border area due to requests for help from the Department of Homeland Security.
A U.S. defense official told VOA Mattis will visit McAllen, Texas, where about 1,000 U.S. troops are deployed.
The U.S. troops assigned to help with border security are legally prohibited from engaging in domestic law enforcement, such as arresting migrants crossing the border.