KIEV — German Chancellor Angela Merkel pledged Monday to help Ukraine implement reforms to bring the former Soviet republic into NATO, a prospect strongly opposed by Russia.

As Merkel met with Ukrainian leaders on a one-day visit, Russia criticized Ukraine's energy policy in what appeared to be a reminder of the country's — and Europe's — dependency on Russian oil and gas.

"We are proceeding from the fact that one day Ukraine will become a member of NATO," Merkel told reporters after meeting with President Viktor Yushchenko.

Merkel said Germany and other NATO countries will work with Ukraine on a "navigation plan" to guide it toward membership. In order to join, Ukraine will have to upgrade its army in line with Western military standards, fight corruption and promote civil society.

Earlier this year, NATO denied Ukraine a Membership Action Plan, seen as a roadmap toward joining, but promised eventual membership.

That decision was seen as Russia's success in lobbying Western European countries, mainly Germany and France, who cited hostility toward the alliance among many Ukrainians and the country's main opposition parties, as well as the need for further reform.

The two countries were seen as reluctant to anger Russia, which supplies Europe with some 40 percent of the European Union's natural gas imports.

Merkel, however, stressed that the issue does not concern anyone else.

"It cannot be that other countries that don't belong to the alliance are discussing this issue," Merkel said. "It is a question for Ukraine and NATO."

Merkel also said Ukraine has made strong progress toward further integration with the European Union.

The same day Merkel was in Kiev, officials in Moscow discussed oil and gas relations with Ukraine.

Deputy Prime Minister Igor Sechin criticized Ukraine's plans to reverse the direction of the Odessa-Brody oil pipeline this year, citing concerns over stability of Russian crude supplies to Europe.