Jin Liqun, president-designate of the new Asian Infrastructure Investment Bank, said Wednesday the doors will be kept open for the United States to join the China-led multilateral lender, even though China is not part of the U.S.-led Trans-Pacific Partnership trade pact.

"China is interested in joining the TPP," Jin said after an address at the Brookings Institution in Washington. "Even though, for some reason, China is not part of the TPP, the door remains open for U.S. membership of the AIIB."

Of the gesture, the former deputy finance minister said, "It is a very interesting question: Why do you still welcome the U.S. even though the U.S. rejects China from the TPP? It's very simple. We are inclusive. We are more generous."

His remarks came as U.S. Trade Representative Michael Froman said in a teleconference on Oct. 15 it was premature to discuss China's participation in the TPP framework as the country is far from meeting its high standards.

The United States, Japan and 10 other countries concluded the massive free trade deal covering some 40 percent of global output on Oct. 1.

Jin also signaled that the first batch of projects the AIIB will invest in may be decided as early as next April.

The Beijing-based AIIB is expected to be established by year-end with nearly 60 founding members, mostly Asian economies but also including some major industrialized countries, such as Britain and Germany.