Washington (CNN) — “Good morning, American pilots. We are here to greet you on your Fourth of July Independence Day.”

That was the message two Russian bombers delivered while flying within tens of miles of the California coast this month to the U.S. fighter jets that intercepted them, according to the North American Aerospace Defense Command.

The midair encounter between Russian Tu-95 “Bear” bombers and American F-15s came on the same day that Russian President Vladimir Putin sent congratulations to President Barack Obama for July Fourth.

The Russian pilots used an emergency aircraft communication channel to send the message, a NORAD spokesman told CNN on Wednesday, providing new details about an event first reported earlier this month.

He declined to describe the move as a threat but said the incident was “potentially destabilizing,” because the Russian approach was unannounced and the bombers in question are nuclear capable.Bombers didn’t enter U.S. airspace

American fighters also intercepted two other Russian Tu-95 bombers on July Fourth, off the southern coast of Alaska, according to the U.S. military.

In neither case did the Russian planes enter U.S. airspace, which extends 12 nautical miles from American coastlines, officials said. The U.S. fighters tracked them until they turned around.

The bombers off California flew roughly 40 miles from the state’s central coast, the NORAD spokesman said.

That encounter was more unusual as Russian planes don’t often venture that far south, a U.S. military official told CNN a few days afterward. Russia conducted a similar flight off the West Coast on July Fourth in 2012.

While the intercepts were routine from a military point of view, the U.S. official said, the Pentagon sees them as Putin “sending a message” to the United States on Independence Day.Putin’s official message

In his official message to Obama, Putin expressed confidence that Moscow and Washington could “find solutions” to international issues.

He said that despite differences between the two countries, “Russian-American relations remain the most important factor of international stability and security,” according to a Kremlin statement.

Earlier this year, the Pentagon considered, and then rejected, the idea of stopping routine intercepts of Russian military aircraft flying off Alaska, because the U.S. intercept flights appeared to have limited deterrent or intelligence value, U.S. defense officials told CNN.

CNN’s Brian Todd reported from Washington, and Jethro Mullen in Hong Kong wrote this report. CNN’s Barbara Starr contributed to this report.