The U.S. ruled out strategic collaboration with Moscow in the Middle East and said Russia has built up a ground force inside Syria with heavy weaponry that could support a Syrian army offensive.

Russia escalated its assault on opponents of Bashar al-Assad’s regime with its first naval bombardment on Wednesday. It launched a volley of 26 medium-range cruise missiles from four warships in the Caspian Sea nearly 1,000 miles away.

For the first time since Moscow’s direct intervention in the Syrian conflict a week ago, Russian warplanes and helicopters appeared to be aiding a ground assault by pro-regime forces and militias against rebel forces focused in the central Syrian province of Hama, according to opposition activists and fighters.

The developments add up to a burgeoning Russian military campaign based on land, air and sea that is at odds with U.S. goals, compounding tensions between the two big powers.

The U.S. ambassador to the North Atlantic Treaty Organization, Douglas Lute, said Wednesday that Russia has deployed rocket artillery, its most advanced tanks, air defense systems and attack helicopters. The retired three-star general called the rapid military deployment “quite impressive.” Russia has also built up its naval forces, positioning some 10 ships in the Mediterranean, he said.