BRUSSELS - The European Commission may spare Hungary and Slovakia from an embargo on buying Russian oil, now under preparation, wary of how dependent the two countries are on Russian crude, two EU officials said on Monday.

The Commission is expected to finalise on Tuesday work on the next, and sixth package of EU sanctions against Russia over its actions in Ukraine, which would include a ban on buying Russian oil, because oil exports are a major source of Moscow's revenue.

Hungary, heavily dependent on Russian oil, has repeatedly said it would not sign up to sanctions involving energy. Slovakia is also one of the EU countries most reliant on Russian fossil fuels.

To keep the 27-nation bloc united, the Commission might offer Slovakia and Hungary "an exemption or a long transition period", one of the officials said.

The oil embargo is likely to be phased in anyway, most likely only taking full effect from the start of next year, officials said.

The package is to be presented to ambassadors of EU governments on Wednesday.

(Reporting by Jan Strupczewski, Kate Abnett, Editing by Louise Heavens)