A U.S. Air Force surveillance plane making a routine flight over Russia to fulfill a treaty obligation was forced to make an emergency landing in eastern Russia earlier this week after experiencing a problem with its landing gear, a Pentagon spokesperson told Fox News.

The unarmed American military plane had Russian officials on board as part of the 1992 Open Skies Treaty, which bounds 34 nations, including Russia and the United States, to allow military inspection flights to ensure compliance to long standing arms-control treaties and to offer greater transparency into each nation's military capabilities.

"On July 27, a U.S. Open Skies Treaty observation aircraft took off from Russian airfield Ulan Ude to begin a Treaty observation flight but the aircraft landing gear did not fully retract," Lt. Col. Michelle L. Baldanza, a Pentagon spokesperson, said in an emailed statement to Fox News.

Baldanza said the American surveillance plane landed safely in the city of Khabarovsk on Russia's eastern seaboard to drop off the Russian officials before continuing on to a U.S. air base in Japan.

The U.S. plane was not able to fulfill its mission of photographing Russian military sites, according to the Pentagon.

Russia has not always been as open as the United States in allowing access to its military sites, which include airfields and nuclear silos, according to senior U.S. military leaders.

Russia has placed restrictions on U.S. military flights over Kaliningrad for the last two years where a recent Russian military buildup threatens neighboring NATO-aligned Baltic nations, whom America is bound to defend.

Russian jets from Kaliningrad buzzed a U.S. Navy destroyer repeatedly in the Baltic Sea off the coast of Poland in April, coming as close as 30 feet to the American warship, Navy officials said at the time.

This week, President Obama accused Russia of potentially leading the hack of Democratic National Committee emails that forced the resignation of its Chairwoman Debbie Wasserman-Schultz at the start of the party's convention in Philadelphia earlier this week.

“What we do know is that the Russians hack our systems, not just government systems but private systems,” Obama told NBC.

It was the first time the president publicly accused Russia of conducting cyber warfare against the United States.

In February, the Russians asked their American counterparts if they could install new advanced optical sensors to its cameras for future surveillance flights over the United States, which began in 2002.

Defense officials and Capital Hill lawmakers have expressed their unease with the request which they say will boost Russia's ability to spy on the United States.

The United States relies primarily on satellites to gather intelligence on Russia.

Recent Russian flights in the United States have photographed critical infrastructure such as power plants and internet communication hubs in addition to military sites, all allowed under the Open Skies Treaty according to American defense officials.

“The treaty has become a critical component of Russia’s intelligence collection capability directed at the United States,” Adm. Cecil D. Haney, commander of the United States Strategic Command, wrote in a letter last year to Rep. Mike Rogers (R-Ala.), who heads the House Armed Services subcommittee on strategic forces, according to the New York Times.

Russia conducted five flights over the United States in 2014 as part of the Open Skies Treaty and four more in 2015. This year, Russia is expected to conduct six flights, starting from either Dulles International Airport outside Washington, or Travis Air Force Base in California according to the Pentagon.

In June, three powerful House GOP committee chairmen wrote President Obama voicing concern that Russia has violated the intent of the Open Skies Treaty and are using the flights to "expand its espionage capabilities" against the United States.

“Allowing Russia to upgrade the sensors used in these flights to digital technology would only make this worse… We urge you to heed the advice of senior military personnel and other officials and reject this Russian request while examining modern alternatives to these flights," capabilities,” Chairmen Ed Royce, Devin Nunes and Mac Thornberry said in their letter to Obama last month.

Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel. You can follow him on Twitter: @LucasFoxNews