A leader of a U.S. congressional group dedicated to promoting relations with Japan on Monday voiced eagerness to boost bilateral economic ties despite Washington's withdrawal from the Trans-Pacific Partnership free trade deal.

"Whatever happens with (a possible Japan-U.S. trade deal), we want to make sure that our economic ties remain as strong as they are now and continue to grow," said Democrat Joaquin Castro of Texas, co-chair of the U.S.-Japan Caucus.

Castro was speaking at a reception in Washington for the caucus, a bipartisan congressional organization with more than 100 members.