MOSCOW  Ukraine joined the World Trade Organization on Tuesday after 14 years of negotiations, a milestone for the former Soviet republic that helps clear the way for a valuable free trade agreement with the European Union.

Officials in the Ukrainian capital, Kiev, suggested that the membership represented a coming of age, of sorts, for trade relations of former Soviet countries. The deal is expected to lift living standards and increase investment in Ukraine, one of Europe’s poorest countries.

Ukraine  with a population around 46 million and a gross domestic product estimated by the World Bank at $106 billion  became the largest former Soviet state to join the trade group to date; Russia is negotiating for membership.

“We have difficult homework to do,” President Viktor A. Yushchenko of Ukraine said at a news conference in Geneva, where the W.T.O. is based, as quoted by Bloomberg News. “This starts the colossal integration work that lies ahead.”