Pentagon chief Ashton Carter says the US military is planning to counter Russian “aggression”, accusing Moscow of endangering world order by “brandishing” its nuclear weapons.

"We are adapting our operational posture and contingency plans as we -- on our own and with allies -- work to deter Russia's aggression, and to help reduce the vulnerability of allies and partners," Defense Secretary Carter declared on Saturday.

In remarks at the Ronald Reagan Presidential Library in California, Carter also expressed “deep” concerns about China's growing influence and military power, saying its land reclamation bid in the South China Sea could trigger war in the Asia-Pacific region.  

"The United States joins virtually everyone else in the region in being deeply concerned about the pace and scope of land reclamation in the South China Sea," Carter said.

Russia's 'challenging activities'

But the Pentagon chief reserved his stronger words for the Kremlin, accusing it of being engaged in "challenging activities" at sea, in the air, in space and in cyberspace.

"Most disturbing, Moscow's nuclear saber-rattling raises questions about Russian leaders' commitment to strategic stability, their respect for norms against the use of nuclear weapons, and whether they respect the profound caution nuclear-age leaders showed with regard to the brandishing of nuclear weapons," he said.

Carter said Russia is creating problems for the US both in Europe and the Middle East.

"In Europe, Russia has been violating sovereignty in Ukraine and Georgia and actively trying to intimidate the Baltic states," he said. "Meanwhile, in Syria, Russia is throwing gasoline on an already dangerous fire, prolonging a civil war that fuels the very extremism Russia claims to oppose."

"We do not seek a cold, let alone a hot, war with Russia," he said. "We do not seek to make Russia an enemy. But make no mistake; the United States will defend our interests, our allies, the principled international order, and the positive future it affords us all."

Carter indicated that the US is developing additional new weapons that he said would be "surprising ones I really can't describe here."

Additionally, "we're updating and advancing our operational plans for deterrence and defense given Russia's changed behavior," he stated.

"Finally, we're leveraging other US government capabilities, to include information campaigns to ensure the truth gets through and focused sanctions which have had an impact on Russia," Carter said.

US-Russia ties at lowest ebb

Relations between the United States and Russia are at their lowest point since the end of the Cold War in 1991, largely due to the crisis in Ukraine and Russia’s air campaign against foreign-backed militants in Syria.  

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 Ukraine's crisis.

Moscow says Washington is responsible for the escalating tension in Ukraine through sending arms in support of the Ukrainian army.

On September 30, Russia began its military campaign against militants wreaking havoc in Syria. Moscow has carried out scores of airstrikes, killing hundreds of terrorists. 

US officials have told The Associated Press that Russia has directed parts of its military campaign against US-backed militants and other extremist groups in an effort to weaken them.

They say the CIA-trained militants are under Russian strikes with little prospect of rescue by their American supporters.

Washington’s own doing

In an interview with Press TV earlier this year, an American political and economic scholar said the growing conflict between the United States and Russia over the Ukraine conflict is a result of Washington struggling to maintain its hegemony and making “extremely provocative moves” in Eastern Europe.

“The conflict that Washington has created with Russia is entirely Washington’s doing,” said Dr. Paul Craig Roberts, an economist who served as an assistant secretary of the treasury for economic policy in the Ronald Reagan administration.

US on alert over South China Sea 

Washington says it wants China to reduce tensions in the South China Sea, where Beijing is locked in territorial disputes with its neighbors. Beijing insists Washington must stay out of the row.

On Saturday, Carter said the US was worried about "the prospect of further militarization, as well as the potential for these activities to increase the risk of miscalculation or conflict among claimant states."

China insists it has sovereignty over nearly all of the South China Sea. The Philippines, Vietnam, Malaysia, Brunei and Taiwan also have overlapping claims.

The US does not recognize China’s sovereignty in the disputed waters and has sent surveillance aircraft and warships to monitor Chinese activities.

Washington accuses Beijing of conducting a massive “land reclamation” program in the disputed waters, whereby it has built up rocks and reefs into artificial islands with facilities for potential military use. However, Beijing accuses Washington of meddling in the regional disputes and deliberately stirring up tensions in the region.

On Tuesday, the US Navy sent its USS Lassen, a guided-missile destroyer, within 12 nautical miles of one of China's artificial islands in the South China Sea, a move apparently designed to increase tensions with Beijing.

Moments later, Carter told his Chinese counterpart Chang Wanquan in Kuala Lumpur that the US military would continue to operate in the South China Sea.

In similar remarks on Tuesday, the head of the US Pacific Command said in Beijing that the United States will continue to patrol the waters surrounding China’s man-made islands in the disputed waterway.

US engaged in 'vainglorious attempt'

On Saturday, Carter said the United States has been shifting its focus toward the Asia-Pacific, where the Pentagon is sending its best naval and other military weapons and warships.

"We are also changing fundamentally our operational plans and approaches to deter [Chinese] aggression, fulfill our statutory obligations to Taiwan, defend allies, and prepare for a wider range of contingencies in the region than we have traditionally," he said.

According to an American political pundit, the United States is engaged in a “vainglorious attempt” to project its naval power into the South China Sea, but Beijing will not fall into Washington’s trap.

“These actions, which were conducted with the expressed approval of President Obama, are a display of intemperate oneupmanship by the US Navy and a vainglorious attempt to project US power into the South China Sea,” said Dennis Etler, a professor of Anthropology at Cabrillo College in Aptos, California.

“While the US acts like an impetuous adolescent, goading China to a fight, China is playing the role of the mature adult in this misadventure, willing to let the transgression go with a simple admonition,” he told Press TV on Tuesday.