U.S. President Barack Obama said the European Union and United States must move forward with a free-trade accord, the Transatlantic Trade and Investment Partnership (TTIP), still under negotiation that supporters say could boost each economy by some $100 billion.

"It is indisputable" that free trade has strengthened the U.S. economy and also has brought enormous benefits to countries that engage in it, Obama said. 

The U.S. president spoke at a news conference with German Chancellor Angela Merkel, one of his closest allies in dealing with a shaky global economy and security crises in the Middle East and Ukraine.