MEXICO CITY, Nov. 22 (Xinhua) -- Mexico continues to lobby the United States to scrap steep new tariffs on steel and aluminum imports, before the trade partners sign an updated free trade agreement later this month, an official source said on Wednesday.

"We are working to find a solution. We have the arguments, we have presented alternatives in terms of how we can solve this, and we hope to resolve it before Nov. 30," Kenneth Smith, Mexico's head negotiator to the trade agreement, told reporters.

The agreement -- an updated version of the North American Free Trade Agreement (NAFTA) between Canada, Mexico and the United States that is now called the United States, Mexico, Canada Agreement (USMCA) -- is expected to be signed by the three parties on the sidelines of the upcoming G20 leaders summit, which begins on Nov. 30 in Argentina.

In June, the United States imposed a 25 percent tariff on steel and 10 percent tariff on aluminum imported from Mexico and other countries.

"There's a chance we can do it," said Smith of having the tariffs repealed, "but we don't have a 100-percent guarantee."

Negotiations on the USMCA were finalized at the end of September following year-long talks. The document is now being reviewed by each country's legislature for approval.

"The agreement could ... take effect by Jan. 1, 2020," said Smith.

U.S. President Donald Trump demanded that NAFTA be renegotiated to secure a better deal for U.S. industry. In the process, new chapters were added on e-commerce and other developments that were not economic factors back when NAFTA was signed in 1994.