WASHINGTON — US and Russian fighter pilots communicated directly in the skies over Syria on Tuesday in a successful test of new procedures for avoiding incidents as they pursue separate air campaigns, the Pentagon said.

Navy Capt. Jeff Davis said the test, carried out between one aircraft from each side over south central Syria, lasted three minutes and "met its intended objective."

"This test assured that the first time this mode of communication was used would not be during an unplanned encounter," Davis said.

The United States and Russia signed a "memorandum of understanding" on Oct. 20 aimed at de-conflicting their air operations over Syria, where they are waging parallel air campaigns with different objectives.

A US-led coalition has been targeting Islamic State forces with airstrikes since December 2014, while the Russians have been hitting a broader range of rebels since opening an air campaign in September in support of its Syrian ally, President Bashar al-Assad.

Over the past two months, the pace of US airstrikes has fallen off, compared to the previous six months, hitting a low of 117 airstrikes last month.

The Pentagon denies the drop-off is related to Russia's entry in the conflict, attributing it instead to fluctuations typical of military operations.

US Defense Secretary Ash Carter last week vowed to intensify coalition airstrikes against the IS group, which has taken over large swaths of territory in Iraq and Syria.

A US defense official said Tuesday's test did not amount to joint training with the Russians, as Moscow has described it in a statement.

"We put on hold all military to military cooperation following the onset of Russian aggression in Crimea, and that remains in effect," the official said, speaking on condition of anonymity.

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