German Foreign Minister Frank-Walter Steinmeier, whose country holds the rotating EU presidency, was joined by representatives from the European Commission and Council for the formal start of negotiations during a one-day visit to Kiev on Tuesday.

Prime Minister Viktor Yanukovich promised to press on with political and economic reforms to foster closer ties with the EU. But he expressed frustration that foreign ministers from the bloc last month had stopped short of promising Ukraine membership one day.

"There was a certain amount of disappointment among citizens of Ukraine," he said at a joint press conference with Steinmeier.

He added that the bloc should remain open to all European states that "respect the rule of law."

Steinmeier assured Yanukovich that the EU considered Ukraine a "unique and important country" in its neighborhood policy, which calls for closer ties with states to the east and south of the bloc.

Contingent on reforms

The two officials failed to announce a timeframe for the negotiations, but Yanukovich said he was aware that the pace of Ukrainian reforms was key.

"We hope that we will be able to negotiate over a new enhanced agreement in a speedy and efficient way," he said.

The EU partnership and cooperation agreement with Ukraine will replace a treaty that was signed in 1998 and is due to expire next year. It will allow stronger cooperation on security policy, justice issues, gas and oil transit and visa policy as well expanding free trade between Ukraine and the bloc.

The final component is dependent on Ukraine joining the World Trade Organization, which Yanukovich said should happen by mid-2007.

The EU is keen to promote the "Western orientation" of Ukraine, which has been embroiled in a power struggle between pro-Russian and pro-Western forces since its so-called "orange revolution" in 2004.

EU divided over Ukraine joining

But the issue of whether the new pact will include the prospect of eventual EU membership for Ukraine has divided the bloc.

EU foreign ministers papered over the differences in conclusions of a Brussels meeting last month, saying that the bloc remained committed to supporting Ukraine's democracy, stability and prosperity and "wishes to reinforce this commitment through a new enhanced agreement." They acknowledged Ukraine's "European aspirations" but said that "a new enhanced agreement shall not prejudge any possible future developments in EU-Ukraine relations."

Britain, Hungary, Poland and Sweden support Kiev's ambition to join Europe's rich club. But a number of the 27 current member states -- including Germany, France and Spain -- are fiercely opposed.

Ukrainian President Viktor Yushchenko has pressed for accession talks to start next year, but EU leaders said at the last EU-Ukraine summit, in October, that the country has not undertaken enough reforms to be a contender.