Republican senators are warning President Trump: Be very careful on NAFTA.

Trump was ready to rip up the 23-year-old free trade deal with Canada and Mexico last week before phone calls with his counterparts from the two countries, a slew of leaders and advisers from Congress, and his own cabinet intervened to calm the president down. Now Trump says he'll "renegotiate" instead.

GOP leaders are still worried.

"It goes without saying that free trade has been a cornerstone of the economy in Texas," Senator John Cornyn of Texas, the Republican Whip, said this week.

Texas is the most dependent state on NAFTA. It's also a Republican stronghold.

It's not alone. Seven of the 10 states that export the most to Mexico and Canada voted for Trump, underscoring just how much is at stake with this deal.

Related: Millions of Americans are still unemployed

Another reason behind Trump's change of heart on NAFTA was farmers. The Washington Post reported that Agriculture Secretary Sonny Perdue walked into his office with a map of the US highlighting the places that would be hardest hit. Perdue noted how many of them voted for Trump.

Trump was likely staring at Ohio, Pennsylvania and Michigan. Those three swing states that sealed his victory are among the top 10 states that depend on NAFTA.

CNNMoney reached out to Republican senators from states that have the most to lose. Almost all say this: They support "modernizing" NAFTA, but they've warned the Trump administration not to erect trade barriers.

In the words of one GOP senate staffer, any updates must be "done in a targeted and specific manner in conjunction with job creators who currently rely on NAFTA." Here are the top 10 states that export the most to America's neighboring countries.

1. Texas (voted for Trump)
2. California
3. Michigan (voted for Trump)
4. Ohio (voted for Trump)
5. Illinois
6. Indiana (voted for Trump)
7. New York
8. Pennsylvania (voted for Trump)
9. Tennessee (voted for Trump)
10. Arizona (voted for Trump)

The jobs at stake

Exports are one way to look at which states have the most to lose if NAFTA goes away. The other is jobs. About 14 million jobs are on the line, according to the US Chamber of Commerce.

The Chamber has done the most comprehensive look at how many jobs in each state depend on trade with Mexico and Canada. They even isolated how many of those jobs depend specifically on NAFTA, meaning they likely would not exist without the free trade deal.

1. California (575,190 jobs)
2. Texas (387,067 jobs. Voted for Trump)
3. New York (318,169 jobs)
4. Florida (285,754. Voted for Trump)
5. Illinois (211,377 jobs)
6. Pennsylvania (206,209 jobs. Voted for Trump)
7. Ohio (187,968 jobs. Voted for Trump)
8. Georgia (155,397. Voted for Trump)
9. North Carolina (152,422 jobs. Voted for Trump)
10. Michigan (146,985 jobs. Voted for Trump)