The Pentagon confirmed a potentially dangerous close call that occurred between a Russian fighter jet and an American reconnaissance plane over the Pacific six weeks ago that brought the planes to within about 100 feet of each other. The incident occurred around the time that U.S. tensions with Russia because of the situation in Ukraine were at their peak.

Pentagon spokesman Col. Steve Warren told reporters Tuesday the close call occurred on the afternoon of April 23 when a Russian Su-27 "Flanker" fighter jet intercepted a U.S. Air Force RC-135U reconnaissance aircraft in international airspace over the Sea of Okhotsk. That body of water is situated between the eastern Russian mainland and the Kamchatka Peninsula.

According to Warren, the Russian fighter approached the RC-135U "across the nose of the US aircraft, within approximately 100 feet."

"Our senior leadership in the department have communicated our concerns over that incident directly the Russian government." Warren said. Defense Secretary Chuck Hagel and chairman of the Joint Chiefs Gen. Martin Dempsey had both communicated their concerns to their Russian counterparts, though he did not know in what form.

Warren said there were no radio communications between the two aircraft or any other type of non-verbal communication. He did say that "there was some maneuvering by the Flanker, he kind of turned a little bit to expose its belly to the RC-135u." Though it's hard to understand the intent of that move Warren said that because of the maneuver the crew aboard the American plane was able to see that the Russian aircraft was armed.

Warren said he's not aware of any other similar incidents since this incident and that American aircraft are continuing to conduct normal flight operations.

The Air Force has only two RC-135U's in its inventory, the aircraft are essentially Boeing 707's that carry specialized equipment able to monitor land, air and sea radar signals.

Meanwhile the Russian withdrawal of 40,000 troops that had massed along the border with Ukraine is almost complete. Warren said the majority of the forces have re-positioned away from the border with less than a 1,000 Russian troops still there.