German Chancellor Angela Merkel and US President Barack Obama also attended the opening of the Hannover Trade Fair, the world's largest for industrial technology. Both leaders once again emphasized the significance of completing TTIP negotiations in 2016.

U.S. President Barack Obama (L) and German Chancellor Angela Merkel attend a press conference in Hannover, Germany, April 24, 2016. Barack Obama arrived in Hannover on April 24. He will attend the opening ceremony of Hannover industrial fair and hold talks with German Chancellor Angela Merkel. (Xinhua/Zhang Fan)

"This agreement, TTIP, is an agreement that sets standards in a very particular way. Therefore I want to speak out here very clearly in favour of taking the chance in the window of time we have. There won't be another opportunity like it any time soon and let us therefore work together on this," Merkel said.

"T-TIP will eliminate terrace, simplify procedures, bridge differences in regulations and cut red tape. All of which will make it easier to invest and trade. But time is not on our side. If we don't complete negotiations this year then upcoming political transitions in the United States and Europe could mean this agreement won't be finished for quite some time," Obama said.

Merkel and Obama insisted that the US and EU should keep pressing for the transatlantic free trade deal. Supporters say the accord could boost the US and European economies by some $100 billion each. TTIP is primarily a deal to cut tarriffs and regulatory barriers to trade between the US and the EU countries. It aims to make it easier for companies on both sides of the Atlantic to access each other's markets. The negotiations are planned to be finalized by the end of 2014, but since the US and EU still diverge on a number of issues, negotiations have been on and off over past years.