1147 GMT July 16, 2018
"We will deploy whatever capability is necessary here," Mattis said on Wednesday when asked about regional air defenses at a press conference with Lithuanian President Dalia Grybauskaite in Vilnius.
His remarks came after two US military officials earlier said the Pentagon was considering deploying a Patriot missile battery to the Baltic region ahead of NATO military maneuvers there this summer.
Last year, Russia deployed nuclear-capable Iskander-M missiles to the country’s westernmost region of Kaliningrad, near its border with the Baltic countries and NATO member states.
Kaliningrad is sandwiched between Lithuania from the north and east and Poland from the south. The Baltic Sea is on the region’s west.
Wary of the US-led NATO alliance’s military buildup near its borders, Russia is preparing for massive military exercises in its western military region in September.
Mattis on Wednesday condemned Russian moves. "Any buildup of Russian combat power in an area where they know, and we all know, they are not threatened by anything that we are doing ... is simply destabilizing," he said.
The Pentagon chief refused to clear whether US Patriot missiles would be deployed to Lithuania permanently or temporarily.
"We will make those decisions in consultation with the Lithuania government," he said.
"Everyone knows this is not an offensive capability," Mattis said, referring to Patriot missiles.
Relations between Washington and Moscow have been strained largely due to the Ukraine crisis. The US and its allies accuse Moscow of sending troops into eastern Ukraine in support of the pro-Russian forces. Moscow has long denied involvement in the crisis.
The ties further deteriorated when Moscow in September 2015 launched an air offensive against Daesh terrorists in Syria, many of whom were initially trained by the CIA to fight against the Syrian government.
Russia has accused the US of taking hostile actions against Moscow.
The Russian military has also warned the Pentagon against conducting airstrikes on Syrian military positions, noting that its S-300 and S-400 air defense systems in Syria are active.
In addition, Moscow has suspended a series of nuclear deals, including a symbolic pact to cut stocks of weapons-grade plutonium in both countries.