A broad new trade treaty struck between the European Union and Ukraine will take full effect from September, the European Council said on Tuesday on the eve of an upbeat summit in Kiev.

"This is the final step of the ratification process through which the EU and Ukraine commit to a close, long-term relationship in all main policy areas," it said in a statement.

Many provisions of the deal were already operating on a provisional basis, it said, adding that the its conclusion would bring a "new impetus to the cooperation".

Council President Donald Tusk and European Commission President Jean-Claude Juncker will meet Ukrainian President Petro Poroshenko for the 24-hour summit, starting with a dinner on Wednesday in Kiev.

Poroshenko voiced confidence on Tuesday that the second-biggest ex-Soviet state would move closer to membership of the EU and the NATO defense alliance -- although neither body sees that as remotely likely in the coming years.

"I am confident we will win," Poroshenko said in a statement. "Ukraine will definitely be in the family of European nations, both in the European Union and in NATO."

A senior EU official said that the summit was expected to be upbeat in tone: "This is a very positive moment in our relationship," he said, noting that a long-standing ambition for Ukrainians to have visa-free access to the EU had become a reality last month for those with modern, biometric passports.

However, Ukraine still has much to do to reform Soviet-era administration and infrastructure to bring it closer into line with its western neighbors and to curb corruption, he added.

The summit agenda covers Ukrainian reforms and the implementation of the trade and association pact, security in Ukraine - notably the peace process with Russia over the conflict in the east - and regional and foreign policy matters.

The EU and Ukraine have been concerned that President Donald Trump could scale back U.S. support for Ukraine in the interests of improving ties with Russia. But EU officials and Poroshenko welcomed as a sign of support Trump's appointment at the weekend of a special envoy for Ukraine as well as a visit to Kiev on Sunday by U.S. Secretary of State Rex Tillerson.

Poroshenko welcomed NATO Secretary General Jens Stoltenberg on Monday and said Kiev would work on a membership plan, something Moscow said would not promote stability.