BRUSSELS/KIEV: European Union nations will decide on new sanctions against Moscow by Friday, with Russian aggression toward Ukraine requiring the strongest possible response, incoming EU foreign affairs chief Federica Mogherini said.

Leaders of the 28-member EU decided on Saturday to impose a fresh round of sanctions against Russia after alleging that Moscow had deployed troops and weapons to back a rebel counteroffensive in southeast Ukraine.

Mogherini, currently the Italian foreign minister, said the European Commission, the bloc’s executive, would present a package of new tougher measures to ambassadors in Brussels as soon as Wednesday.

The EU ambassadors are “meeting again tomorrow, Thursday and Friday, and by Friday a decision will be adopted,” she told reporters after meeting European parliamentarians following her nomination as EU diplomatic chief on Saturday.

She said the sanctions would be in the four areas — financial sanctions, arms, dual-use materials and technology — targeted by earlier rounds of sanctions.

A Ukrainian official said Tuesday that Russian forces have been spotted in both of the major rebel-held cities in eastern Ukraine.

The claim by Col. Andriy Lysenko, a spokesman for Ukraine’s national security council, came as the country’s defense minister said Ukraine’s armed forces are expanding their strategy from just fighting separatist rebels to facing the Russian army in a war that could cost “tens of thousands” of lives.

Lysenko told reporters that Russian troops had been seen in the cities of Donetsk and Luhansk, as well as other locations throughout the east, but he did not give details and the claim could not be confirmed independently. Lysenko also said 15 servicemen had been killed over the previous day.

In Moscow, a Kremlin aide sharply criticized EU Commission President Jose Manuel Barroso for breaching confidentiality when he quoted President Vladimir Putin as saying Moscow could take over Kiev in two weeks, if it wished.

Yuri Ushakov, the Russian leader’s foreign policy adviser, told reporters that Putin’s statement was “taken out of context and carried a completely different meaning.”

Ushakov lashed out at Barroso, saying it was a breach of diplomatic practices and “unworthy of a serious politician” to speak publicly about a private conversation.