WASHINGTON — The Pentagon said Monday that Defense Secretary James Mattis is "completely aligned" with President Donald Trump's seemingly abrupt announcement to pull the U.S. out of an arms control treaty with Russia.
"The secretary of Defense has consistently said that Russia has not been in compliance with the treaty," Pentagon spokesman Col. Rob Manning said. "The secretary is completely aligned with the president, and he is in close contact with the president on this."
Earlier this month, Mattis told reporters in Brussels that any decision to withdraw from the Intermediate-Range Nuclear Forces, or INF, treaty would be done in consultation with NATO partners since Russian missiles pose an immediate threat to allies in the region.
"This will be a decision obviously made in concert with our allies by the president," Mattis said at the time. "We are trying to bring them [Russia] still back into compliance. And now is the time. It's gone on long enough."
When asked whether Mattis coordinated with NATO counterparts in the wake of Trump's announcement, the Pentagon directed the query to the White House. The White House has yet to respond to CNBC's request for comment.
Over the weekend, Trump said it was "unacceptable" for the U.S. to continue to adhere to the Intermediate-Range Nuclear Forces Treaty while Russia and China pursue nuclear weapons.
The 1987 treaty, signed by Russia and the U.S., prohibits the production or testing of ground-launched cruise missiles with a range of approximately 300 to 3,400 miles.
"If Russia's doing [it], and China's doing it, and we're adhering to the agreement, that's unacceptable," Trump said.
"Russia has not adhered to the agreement, so we are going to terminate the agreement, and we are going to develop the weapons," Trump added. "If they get smart, and others get smart, and they say, 'Let's not develop these horrible nuclear weapons,' I would be extremely happy with that. But as long as somebody is violating that agreement, then we are not going to be the only ones to adhere to it."
A spokesperson for the Kremlin said Monday that if the U.S. withdraws from the treaty and begins developing new missiles, then Russia would be forced to do the same.
Dmitry Peskov told reporters that Trump's announcement is a "cause for deep concern" and would "make the world a more dangerous place." He added that the decades-old treaty would be raised at talks with U.S. national security advisor John Bolton this week.
Mikhail Gorbachev, the former president of the Soviet Union, criticized Trump for threatening to withdraw from the nuclear disarmament treaty, saying the move "is not the work of a great mind."
"Do they really not understand in Washington what this can lead to?" Gorbachev reportedly told Russian news agency Interfax on Sunday, adding that the decision "will undermine all the efforts that were made by the leaders of the USSR and the United States themselves to achieve nuclear disarmament."
Gorbachev added that "all agreements aimed at nuclear disarmament and the limitation of nuclear weapons must be preserved for the sake of life on Earth."
— CNBC's Holly Ellyatt in London contributed to this report.