Two U.S. Navy aircraft carrier battle groups and a Marine Corps air-ground task force have reportedly begun operating in the Western Pacific.

The move is aimed at inflicting psychological pressure on China in its territorial disputes over East China Sea islands which China calls Diaoyu and Japan calls Senkaku, according to reports on Wednesday.

Tensions have risen in recent months over the islands, which lie in rich fishing grounds and on key shipping lanes. The seabed in the area is also believed to harbor mineral reserves.

The naval expeditionary strike groups have just completed a U.S.-Japan island defense exercise near Guam.

TIME magazine reported U.S. navy officials have confirmed the USS George Washington carrier strike group has begun operating in the East China Sea. And the USS John C. Stennis group is only slightly further away in the South China Sea.

Each aircraft carrier is armed with more than 80 warplanes, and strike groups typically include guided-missile cruisers and destroyers, submarines and supply ships.

In the nearby Philippine Sea, some 2,200 Marines are embarked aboard the USS Bonhomme Richard amphibious assault ship and two frigates. The Marines are equipped with amphibious assault vehicles, light armored vehicles, artillery, helicopters and Harrier fighter jets.

Meanwhile, Chinese government ships entered territorial waters off the islands for the second straight day, Japanese coastguards said.

Three maritime surveillance ships “ignored warnings from patrol vessels of our agency... and entered our country’s territorial waters” shortly after 12:30 p.m. Korean time, the coastguard said in a statement.

“Our patrol vessels are demanding they leave our country’s territorial waters by radio and other means but the Haijians have not replied,” it said, referring to the ships’ names.

The Chinese ships were among four vessels that had been in island waters on Tuesday, remaining for around six hours, despite demands from Japan that they leave.

Diplomats from China and Japan traded insults at the United Nations in New York last week and sometimes violent demonstrations in Chinese cities hit Japanese business interests in the country last month.

Christine Lagarde, head of the International Monetary Fund, in an interview published Wednesday voiced concerns over the spat, warning the shaky world economy could not afford for the two economic powers to be so distracted.

(From news reports)