U.S. President Barack Obama will meet Ukraine's president-elect next week during a European tour aimed at shoring up regional security amid reports that a second team of European monitors went missing in the country's restive east.

The meeting in Warsaw will come less than two weeks after pro-European Petro Poroshenko, a chocolate tycoon, was elected in the shadow of a showdown between Washington and Moscow over the fate of Ukraine that has brought relations to their lowest level since the Cold War.

U.S. President Barack Obama will meet Ukrainian president-elect Petro Poroshenko in Poland on Wednesday, a U.S. official said.

The meeting will take place during a trip by Obama -- also including stops in Belgium and France -- designed to underscore the U.S. security commitment to eastern Europe following Russia's annexation of Crimea, said U.S. Deputy National Security Adviser Ben Rhodes.

U.S. President Barack Obama said Friday his press secretary Jay Carney was stepping down after more than three years as the first line of defense for his administration.

Obama interrupted Carney's daily press briefing to announce that his spokesman had resigned and would be replaced by his deputy Josh Earnest.

South Korea gave a guarded response Friday to a Japanese deal to ease sanctions against North Korea, stressing the need to maintain a united front against Pyongyang's nuclear weapons program.

Japanese Prime Minister Shinzo Abe announced Thursday that Tokyo would relax some sanctions if North Korea delivers on a pledge to reinvestigate the cases of Japanese nationals kidnapped to train spies.

Syria's opposition National Coalition welcomed a pledge from U.S. President Barack Obama on Wednesday to ramp up support for rebels fighting the Damascus regime of Bashar Assad.

"This additional support highlights the partnership between the United States and the Syrian people in ending the humanitarian disaster and putting Syria on the path to genuine democratic transition," the bloc's U.S. representative, Najib Ghadbian, said in a statement.

President Barack Obama mounted a defiant defense of his global leadership Wednesday, rebuking critics who see him as weak but warning that not every global threat justifies a U.S. military response.

In a major speech at the West Point military academy, Obama denied U.S. power had ebbed under his watch, after he withdrew troops from Iraq and as he does the same in Afghanistan.

President Barack Obama mounted a defiant defense of his global leadership Wednesday, rebuking critics who see him as weak but warning that not every global threat justifies a U.S. military response.

In a major speech at the West Point military academy, Obama denied U.S. power had ebbed under his watch, after he withdrew troops from Iraq and as he does the same in Afghanistan.

U.S. President Barack Obama will authorize U.S. troops to train selected Syrian rebels, in order to counter the rising power of al-Qaida-linked extremists, a U.S. newspaper reported Tuesday.

The White House did not confirm or deny the plan, but said it was "constantly considering available options to combat the terrorist threat emanating from Syria and to facilitate an end to the crisis."

President Barack Obama has postponed a review of U.S. deportation policy for undocumented workers, hoping to give legislative reform a better chance, a White House official said Tuesday.

U.S. President Barack Obama on Tuesday launched a push to get girls interested in science and technology, warning the country would miss out if it did not attract women to those fields.

"There's so much talent to be tapped if we're working together," Obama said at the annual White House Science Fair, where students from elementary to high school present winning projects.