LONDON (Reuters) -Brazil's secretary of foreign trade warned on Thursday in the wake of U.S. President Donald Trump's auto tariffs announcement that global trade was at risk of being 'weaponised' and that World Trade Organization strains were likely to get worse before they get better.

"We didn't need to wake up to what was announced last evening," Tatiana Prazeres, said about Wednesday's move by Trump to impose a 25% tariff on all cars and trucks and major parts like engines and transmissions imported into the United States.

Prazeres, who was speaking via video link at a global trade conference at London's Chatham House think tank, also hit out at the increasingly aggressive approach now being adopted by nations such as the U.S.

"What we see today is that trade is being used as a power tool so it is a big risk of trade being increasingly weaponised," she added. "We don't know where this will lead us."

On its part, the Latin American country remains committed to both multilateralism and the WTO, she said.

Brazil's President Luiz Inacio Lula da Silva has already vowed to lodge a complaint with the WTO over the 25% tariffs Trump slapped on Brazilian steel earlier this month.

"I don't think at this time we have the opportunity of promoting major changes," Prazeres said, referring to the global trading system. "I think it might get worse before it gets better."

Prazeres also said that Brazil was looking to build new trade "coalitions" and "defend our rules-based trade relations with countries that were willing to do so."

"We are looking into expanding our network of trade agreements," she said, highlighting December's European Union and South American Mercosur bloc free trade deal as an example.

"We are willing to promote trade-based rules, we are willing to seek predictability and stability."

(Reporting by Marc Jones, Editing by Louise Heavens and Muralikumar Anantharaman)