The United States recognizes Russian-held islands off Japan’s northernmost main island as belonging to Japan, a U.S. official said Wednesday, speaking in connection with Russian military drills conducted in the disputed territory earlier this week.

“The United States recognizes Japanese sovereignty over these islands,” Marie Harf, a State Department spokeswoman, told reporters, reiterating the U.S. position on the territorial dispute between Tokyo and Moscow.

Harf did not comment directly on Russia’s latest military exercises on Kunashiri and Etorofu islands — part of what Tokyo calls the Northern Territories — off Hokkaido. Russia refers to the islands as the Southern Kurils.

Russia began the drills on Tuesday, mobilizing more than 1,000 troops, five attack helicopters and over 100 vehicles, according to Russian news agency Itar-Tass.

Tokyo lodged a protest Wednesday with Moscow over the drills, which Prime Minister Shinzo Abe described as “totally unacceptable.”

The military exercises on two of the four disputed islands came despite an earlier request by Tokyo, submitted via diplomatic channels, that they be canceled, the Foreign Ministry said.

“The Northern Territories are an inherent part of Japan’s territory, and we cannot accept the move,” a senior ministry official also said, a day after Russia announced the start of the exercises.

The spat over the Northern Territories, which also include Shikotan, and the Habomai islet group, has prevented Tokyo and Russia from signing a peace treaty.

The islands were seized by the Soviet Union following Japan’s surrender in World War II on Aug. 15, 1945.

Abe has attempted to secure the return of the disputed islands by building a personal relationship of trust with Russian President Vladimir Putin, who has come under international pressure since Moscow’s annexation of Crimea.

Russia’s Interfax news agency reported Tuesday that the drills are aimed at defending remote islands.

A Russian Foreign Ministry official said “the drills are not directed against other countries including Japan” and Japan’s protest is “groundless,” the news agency said.

Russia alone makes the decision on holding an exercise in what has become its territory as a result of World War II, the official said.

Japan has been on guard against Russia’s move to expand its military activities in the Far East, with the Defense Ministry underscoring in its white paper last week its oft-repeated position that Tokyo does not accept any attempts to change the status quo by force.

The military drills came days after Japan imposed additional sanctions on Russia for undermining Ukraine’s sovereignty and supporting pro-Russian separatists following the downing of Malaysia Airlines Flight MH17 in July.