ISTANBUL — Russia is offering to mediate with Turkey in a dispute over energy exploration in the eastern Mediterranean Sea after Turkish President Recep Tayyip Erdogan questioned the European Union’s sincerity on resolving a bitter row with members Cyprus and Greece.

Turkey has long been at odds with neighboring Greece and arch foe Cyprus over what demarcates maritime borders in the Mediterranean and Aegean Seas. Now, a Turkish seismic research ship backed by naval warships is exploring in the disputed waters, pitching tensions to their most dangerous levels in decades.

Foreign Minister Sergey Lavrov said at a news conference after meeting Cyprus President Nicos Anastasiades in Nicosia on Tuesday that Russia was prepared to step in to “resolve differences through dialogue and within a legal framework,” should it be invited to do so.

A Russian entry into the eastern Mediterranean fray follows months of attempts by the European Union, led by Germany, to defuse tensions. Russia enjoys good relations with both Ankara and Nicosia and is involved in energy projects across the eastern Mediterranean, but Moscow’s interventions could complicate the European-led process. The United States, embroiled in an acrimonious election campaign, is conspicuous in its absence.