MOSCOW (Reuters) – Russia will retaliate against the United States in a row over a treaty that allows both states to conduct military observation flights over each other’s territory, Russia’s deputy foreign minister said, Russian news agencies reported on Wednesday.

In the latest sign of escalating tensions between the two countries, the United States has accused Russia of flouting the so-called Open Skies Treaty, an agreement designed to build confidence between the two countries’ militaries, and said it plans to take measures against Moscow.

The Wall Street Journal newspaper reported on Tuesday that would include restricting Russian military flights over American territory in response to what it said was Moscow preventing U.S. observation flights over its heavily militarized Baltic exclave of Kaliningrad.

Russian news agencies cited Russian Deputy Foreign Minister Sergei Ryabkov on Wednesday as saying that Moscow was itself unhappy about Washington’s compliance with the same treaty and would take its own measures against the United States in response to any new U.S. restrictions.

“I have no doubt there will be a (Russian) response,” agencies cited Ryabkov as telling reporters.

“But before announcing something on this, we have to analyze the situation with our military and look at how we’ll respond to the Americans.”

Ryabkov was quoted as describing Washington’s approach to the disagreement as one-sided and as saying Russia would not yield to U.S. pressure for it to make concessions.

U.S. Marine General Joseph Dunford, chairman of the military’s Joint Chiefs of Staff, told a Senate Armed Services Committee on Tuesday that Washington believed it would be best if the Open Skies Treaty with Russia continued, but that it should not be in place if Moscow was flouting it.

(Reporting by Maria Kiselyova/Andrew Osborn; Editing by Christian Lowe)