Mexico's presidential front-runner launched his campaign close to the U.S. border on Sunday, demanding respect for Mexicans hours after U.S. President Donald Trump again threatened to scrap a key trade pact and erect a wall between the countries.

Striking a nationalistic tone, Andres Manuel Lopez Obrador signaled that if he won the July 1 election, he would be less accommodating toward Trump than the ruling Institutional Revolutionary Party, or PRI, which has lagged in opinion polls over its failure to contain violence and corruption.

"Mexico and its people will not be the pinata of any foreign government," Lopez Obrador said in a speech to thousands of people who jeered and swore at the mention of Trump. The U.S. president is almost universally disliked in Mexico.