After a tit-for-tat series of delays, the United States conducted an Open Skies Treaty intelligence flight over Russian territory on Monday, a State Department official said.
The spy flight originally was scheduled for April 14 but was canceled by Russia after a U.S. team for the flight failed to arrive near Moscow on time and Moscow refused temporarily to reschedule it.
A Russian Foreign Ministry spokesman also expressed anger on Monday over U.S. delays in certifying a new high-tech Russian aircraft to be used for spying missions over the United States under the Open Skies Treaty that permits limited legal spying over U.S. and Russian territory.
The State Department official said, however, that last week's delay was the result of bad weather – despite radar images showing mostly clear skies over of Russia during the period of last week's planned flight.
"The U.S. Open Skies mission dated April 14 was delayed due to weather conditions beyond the time permitted by the treaty," the official said in a statement. "The flight was rescheduled and on April 21, the U.S. Open Skies Treaty aircraft began its mission in the Russian Federation."
The official said the treaty permits the country conducting the surveillance flight to postpone the flight for 24 hours, "after which the host country is permitted to cancel the mission."
Earlier, the official did not mention that Russia had canceled the April 14 flight or the reasons for the cancelation.
In Moscow, Foreign Ministry spokesman Alexander Lukashevich on Monday defended Moscow's decision to cancel the flight and criticized the United States regarding the treaty, calling the U.S. position "highly non-constructive."
Lukashevich said Russia canceled the April 14 flight by a joint U.S.-Czech Republic team after the team failed to arrive at a meeting point in Kubinka, a town about 40 miles west of Moscow.
Lukashevich made no mention of Monday's U.S. flight, however.
"At the request of the American side of the mission the arrival time was postponed for 24 hours," Lukashevich told state-run ITAR-TASS news agency.
"However, neither the Americans nor the Czechs showed up in Kubinka," he said. "When a new request for a postponement came, we rejected it for good reason, taking into account, among other things, the fact that Russia had already sustained certain costs while waiting for the American observation plane."
Lukashevich said the costs of using Russian resources to support the mission were part of the decision to cancel the mission last week.
The spokesman also noted the U.S. refusal to certify a new Russian Open Skies aircraft for use over the United States as one reason for Moscow's anger at the U.S. overflight last week.
"We have to state with regret that the American side, the only of the parties to the Treaty on Open Skies, has long been adhering to a highly non-constructive position on the examination of our digital observation equipment by putting forth requirements that are not provided for in the treaty," he said.
The Russians want "implementation of the treaty will be safeguarded against the negative impact of considerations of expediency and that its members will strictly abide by their obligations," Lukashevich said.
U.S. intelligence officials and members of both congressional intelligence oversight committees want the Obama administration to block certification of the new Russian surveillance aircraft that are equipped with digital sensors, including advanced radar that allows the aircraft to see through structures.
The White House National Security Council (NSC) deputies committee, a group of senior security officials, met on the issue last week.
An NSC spokesman declined to comment on whether the Russian aircraft had been certified for future Open Skies flights over the United States.
The aircraft are part of a 1992 agreement among 34 nations that allows parties to the treaty to conduct intelligence-gathering flights over national territory. The treaty is a so-called confidence-building measure.
Pentagon and U.S. intelligence officials are concerned the new equipment on the Russian aircraft will permit spying on new and advanced U.S. military capabilities, weapons, and facilities.
The cancellation of the flight last week coincided with the crisis over Ukraine where some 80,000 Russian troops, along with tanks and armored vehicles, are massed near Ukraine's eastern border.
A U.S. official said the cancellation of the flight last week appeared to be part of an effort by Moscow to deny U.S. surveillance of Russian force deployments that appear being readied for a large-scale military intervention in eastern Ukraine.