The Pentagon on Friday rejected a Russian proposal to launch joint air strikes against jihadists from next week in Syria, where they have been conducting separate bombing campaigns.

"We do not collaborate or coordinate with the Russians on any operations in Syria," Pentagon spokesman Navy Captain Jeff Davis told reporters, explaining that Washington and Moscow have separate military objectives.

Iran's supreme leader and president accused the United States of hostility and bad faith Wednesday saying the implementation of its nuclear deal with world powers was not being honored.

Ayatollah Ali Khamenei echoed other officials in Tehran who allege that Washington is creating hurdles for European financial institutions, more than three months after the agreement came into force.

Cuba's Fidel Castro signaled continued resistance to rapprochement between Washington and Havana, writing in an opinion piece on Monday that his country "has no need of gifts" from the United States.

The former president, 89, remained out of sight during last week's historic visit to the communist island by U.S. President Barack Obama which aimed to cement normalization.

China's defenses in the South China Sea are "absolutely necessary", Beijing said Thursday, as it accused the U.S. of militarizing the region.

The defense ministry spoke out as tensions rose between the two powers over reports that Beijing has deployed surface-to-air missiles, fighter jets, and radar installations in the contested region.

The Pentagon on Friday released a small portion of photographs showing injuries suffered by detainees allegedly at the hands of U.S. troops in Iraq and Afghanistan over a decade ago.

Many of the 198 carefully vetted images are close-ups showing cuts, bruises, swollen joints and relatively small wounds. 

The implementation of the Iran nuclear deal marked a major step forward in Washington's cautious rapprochement with Iran, but will further strain ties with Saudi Arabia.

While President Barack Obama's government insists its goal was simply to halt the spread of atomic weapons, experts detect an effort to bring a new balance to its Middle East relationships.

With Saturday's formal implementation of the Iran nuclear deal, the United States lifted it economic sanctions imposed to dissuade Tehran from building a bomb.

Other, separate sanctions designed to punish Iran's alleged sponsorship of foreign militant groups and its ballistic missile program will remain.

The United States will launch a "moonshot" effort to cure cancer, President Barack Obama declared Tuesday, assigning his deputy Joe Biden to lead the effort.

Comparing the scale of the challenge to the successful U.S. mission to put an astronaut on the moon, Obama said the drive would receive the same effort as clean energy research. 

U.S. auto sales touched a new high in 2015 as easy credit, hot new vehicles and strong consumer confidence pushed sales slightly above the record set in 2000, industry data showed Tuesday. 

Some 17.47 million vehicles were sold in the United States last year, nearly 70,000 more than the record set 15 years earlier, according to Autodata. 

U.S. President Barack Obama wept openly Tuesday as he urged America to wake up to the need to tackle the gun violence that claims tens of thousands of lives in the country each year.

Tears streamed down Obama's cheeks as he summoned the memory of the 20 elementary school children slaughtered three years ago in Newtown, Connecticut.