(U.S. Senate) - Senator Jon Tester is continuing his push to better secure the northern border and strengthen national security before a new travel policy between Canada and Mexico begins later this year.

In letters to Homeland Security Director Jeh Johnson and Canadian Ambassador to the United States David MacNaughton, Tester raised questions about a new policy that will allow Mexican travelers to more easily enter Canada.

"I remain concerned that individuals posing as Mexican nationals will attempt to utilize this new policy as a means to more easily travel to the U.S. to do us harm, wrote Tester, Montana's only member of the Homeland Security Committee. "The United States and Canada have long been trusted partners in bolstering each other's national security. Homeland Security cooperating with our Canadian allies is critical to securing our northern border."

Beginning December 1st, Mexican nationals traveling to Canada will now only have to fill out an Electronic Travel Authorization (eTA) that will be linked to the traveler's passport prior to entering Canada. Previously, they had to secure a travel visa in order to visit Canada.

In the letters, Tester also pushed for assurance that both U.S. and Canadian border security agents have access to additional resources and technology to secure the remote areas along the more than 500 mile-long northern border with an influx of travelers from Mexico.

Tester is concerned that this new policy will weaken U.S.-Canadian border protection and leave too many vulnerabilities for international traffickers to illegally move drugs, humans, and goods.

Before the new policy is in place, Tester is urging Secretary Johnson and Ambassador MacNaughton to answer a series of questions-which includes identifying additional resources that will be needed to patrol remote areas of the northern border in Montana, pinpointing additional national security threats that will arise from an increase of travelers from Mexico, and tracking and enforcing security plans for Mexican travelers who overstay the six-months they are granted to visit Canada.

Additionally, Tester is demanding to know what the Canadian vetting procedure will be for granting Mexican travelers with an eTA.

Last year, Tester brought top Homeland Security officials to Montana to tour the northern border and hear firsthand about the issues facing U.S. border officials.

Earlier this year, Congress passed provisions from Tester's bipartisan bill that reformed the Visa Waiver Program to better protect Americans from foreign threats.

Tester's letter to Secretary Johnson is available HERE and the letter to Ambassador MacNaughton is available HERE.