President Trump is on the cusp of the greatest diplomatic victory of his presidency, and probably of the decade. By threatening tariffs against Mexico, he has persuaded its government to take action.

To ward off the tariffs, and to keep alive the hope of free trade between us, Mexico has reportedly pledged to step-up, honor international norms, and do its part to deal with the migrant crisis coming from Central and South America.

If Mexico's offer is as reported, then Trump should take the deal.

According to the Washington Post, if Trump cancels his planned 5% tariff on Mexico, Mexico will adopt a "Safe Third Country" agreement with the U.S. "Safe Third Country" is the principle that asylum-seekers must apply for asylum in the first safe country where they land. In practice, that means Mexico would absorb those fleeing Guatemala, Honduras, and El Salvador. Mexico would stop offloading the burden of this crisis onto the U.S. And those refused asylum in Mexico would not be eligible for asylum in the U.S.

The U.S. already has such an agreement with Canada. Mexico wants to be one of the big three countries in North America, and increasingly it is. That means it needs to pull its weight in handling this crisis.

Additionally, Mexico is reportedly ready to deploy thousands of National Guard troops to the Mexican-Guatemalan border. The more they act like a nation, and not merely a very wide highway to the U.S., the less pressure there is on the U.S. border.

The current pressure, which comes not from Mexicans but from migrants passing through Mexico, is simply too much for the Border Patrol to handle.

For the first time in recorded history, border apprehensions of non-Mexicans have exceeded those of Mexicans. Gang violence in the Northern Triangle region of El Salvador, Honduras, and Guatemala has been fueling the surge, and this deal could all but end the United States' role in the matter.

If there's more Trump wants from Mexico, he should ask later. But at the very least, this act of good faith by Mexico's government should earn them a seven-day delay in 5% tariffs.

It was never realistic that Trump would get Mexico to pay for the wall. But he may have gotten them to do something far better.