MEXICO CITY (Reuters) - Mexico is ready to update the North American Free Trade Agreement with Canada and United States, its foreign minister said on Monday, following a spate of criticism of the accord by Republican presidential nominee Donald Trump.

Foreign Minister Claudia Ruiz Massieu told reporters that since taking effect in 1994, NAFTA has boosted trade, created millions of jobs, drawn investment and made North America more competitive in the global economy.

"However, 22 years later we've also made clear that it's important to be ready to modernize and update this treaty, and we'll be ready to do it if that's what our other two partners in the mechanism suggest doing," she said.

Credited with modernizing the Mexican economy, NAFTA has come under heavy fire from Trump, who has threatened to tear it up if he cannot renegotiate it in his country's favor.

He has complained during the election campaign that Mexico is "killing" the United States on trade.

Bilateral trade between Mexico and the United States is worth around $500 billion a year. Trump has threatened to levy punitive tariffs on goods made in Mexico and China in a bid to bring manufacturing jobs back to the United States.

(Reporting by Dave Graham; Editing by Dan Grebler)