Trump rattled the two nations last week when his administration said he was considering an executive order to withdraw from the trade pact, which has been in force since 1994. He later said he would try to renegotiate the deal first and Kalach said the lobbying effort deserved much credit for Trump's u-turn.
"There was huge mobilization," he said. "I can tell you the phone did not stop ringing in (Commerce Secretary Wilbur) Ross's office. It did not stop ringing in (National Economic Council Director) Gary Cohn's office, in the office of (White House Chief of Staff Reince) Priebus. The visits to the White House from pro-NAFTA allies did not stop all afternoon."
Among those calling the White House and other senior administration officials were U.S. Chamber of Commerce chief Tom Donohue, officials from the Business Roundtable and CEOs from both lobbies, according to people familiar with the discussions.
Mexico has been the prime target of NAFTA critics, who blame it for lost manufacturing jobs and widening U.S. trade deficits. Canada had managed to keep a lower profile, concentrating on seeking U.S. allies in case of an open conflict.
That changed in late April when the Trump administration attacked Ottawa over support for dairy farmers and slapped preliminary duties on softwood lumber imports.
Despite an apparently weaker position -- Canada and Mexico jointly absorb about a third of U.S. exports, but rely on U.S. demand for three quarters of their own -- the two have managed to even up the odds in the past by exploiting certain weak spots.
When Washington clashed with Ottawa in 2013 over meat-labeling rules, Canada retaliated by targeting exports from the states of key U.S. legislators. A similar policy is again under consideration.
Mexico is taking a leaf out of a 2011 trucking dispute to identify U.S. interests that are most exposed, such as $2.3 billion of yellow corn exports.
Mexico is also targeting members of Trump advisory bodies, the Strategic and Policy Forum and the Manufacturing Council, led by Blackstone Group LP's Stephen Schwarzman and Dow Chemical Co. boss Andrew Liveris respectively.
Senior Trump administration officials and Republican lawmakers in charge of trade, agriculture and finance committees also feature among top lobbying targets.
Canada has spread the task of lobbying the United States among ministries, official say, and is particularly keen to avoid disruption to the highly-integrated auto industry.
A core component of Mexico's strategy is to argue the three nations have a common interest in fending off Asian competition and exploring scope to source more content regionally.
The defenders of NAFTA also say that it supports millions of jobs in the United States, and point out that U.S. trade shortfalls with Canada and Mexico have declined over the past decade even as the deficit with China continued to climb.
Part of IQOM's mission is to identify sectors where NAFTA rules of origin could be modified to increase regional content.
For example, U.S., Canadian and Mexican officials are debating how the NAFTA region can reduce auto parts imports from China, Japan, South Korea or Germany, Mexican officials say.
"The key thing is to see how we can get a win-win on the products most used in our countries, and to develop common manufacturing platforms that allow us just to buy between ourselves the biggest amount of inputs we need," said Luis Aguirre, vice-president of Mexican industry group Concamin.