Over seven decades after Japan attacked Pearl Harbour and dragged the United States into a global war, Americans and Japanese overwhelmingly trust each other and are wary of China, an opinion poll has shown.

In contrast to the oft-heard calls from Beijing for more Japanese contrition over World War II, around two-thirds of Americans believe Tokyo has apologised enough or has no need to say sorry.

Conservative U.S. Senator Rand Paul on Tuesday formally launched his 2016 White House bid, the second Republican to join what is expected to be a crowded contest for the party's nomination.

Paul, a conservative libertarian who was elected to the Senate in 2010 with strong support from the Tea Party movement, wasted no time in lashing out at the traditional political establishment, including his own party.

A power outage swept the Washington area Tuesday, hitting the White House, the Capitol and the State Department and knocking out electricity for thousands around the U.S. capital.

Outages stretched from downtown Washington into neighboring Maryland, knocking power out for more than 2,500 people, according to area power companies.

A New York resident has been charged with providing support to Islamic State jihadists in Syria, the Justice Department said Tuesday, after three suspected co-conspirators pleaded not guilty to similar charges.

Brooklyn resident Dilkhayot Kasimov, 26, is charged with "attempt and conspiracy to provide material support to the Islamic State of Iraq and the Levant (ISIL)," the Department of Justice said in a statement, using an alternative name for the Islamic State group.

Conservative U.S. Senator Rand Paul announced Tuesday that he is running for his party's nomination for the 2016 presidential race, making him the second major Republican to join the contest.

"I am running for president to return our country to the principles of liberty and limited government," Paul said on his campaign website.

A judge in North Carolina ruled Monday that prosecutors could seek the death penalty for a man accused of fatally shooting his three Muslim neighbors, U.S. media reported.

Judge Orlando Hudson approved a motion by government attorneys allowing them to pursue a capital murder case against Craig Hicks, the Raleigh News and Observer newspaper reported.

U.S. President Barack Obama has rejected a call by Israel for any nuclear agreement with Iran to be conditional on Tehran's recognition of the Jewish state's right to exist, branding it a "fundamental misjudgement". 

Speaking after Israel proposed its own terms for the accord, Obama told U.S. radio network NPR Monday that demands for Iran to recognize the country go beyond the scope of the agreement.

Republican U.S. Senate majority leader Mitch McConnell on Monday criticized the landmark deal on Iran's nuclear program, confirming that lawmakers opposed to the pact planned a formal response to the agreement.

"The administration needs to explain to the Congress and the American people why an interim agreement should result in reduced pressure on the world's leading state sponsor of terror,"  McConnell said in a statement following last week's marathon talks.

The United States admitted Monday that it has no immediate plans to rescue its nationals stranded in war-torn Yemen and urged them to flee the raging conflict by sea.

State Department spokeswoman Marie Harf could not tell reporters how many American civilians are thought to be caught up in the conflict, as citizens of other nations take to ships.

The co-chair of Turkey's main Kurdish party has accused President Recep Tayyip Erdogan of wanting to set up "a constitutional dictatorship", vowing his movement will strongly oppose moves to impose one-man rule.

Selahattin Demirtas of the People's Democratic Party (HDP) told Agence France Presse that his party hoped to turn Erdogan's political calculations "upside down" in June 7 legislative polls.