U.S. President Barack Obama on Tuesday confirmed the death of Kayla Jean Mueller, who was taken hostage in Syria by the Islamic State group, and vowed to track down her captors.

"No matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for Kayla's captivity and death," he said in a statement.

A U.S. Senate panel voted unanimously Tuesday in support of Ashton Carter to be the new secretary of defense, sending his nomination to a full chamber vote possibly this week.

The Senate Armed Services Committee voted 25-0 to advance the nomination of Carter, a highly-regarded technocrat who is expected to be confirmed to replace outgoing Pentagon chief Chuck Hagel.

U.S. President Barack Obama said Monday there was no reason to extend nuclear talks with Iran once again, stressing the question now is whether Tehran truly wants an agreement.

"I don't see a further extension being useful if they have not agreed to the basic formulation and the bottom line that the world requires to have confidence that they're not pursuing a nuclear weapon," Obama said at a joint press conference with visiting German Chancellor Angela Merkel.

U.S. President Barack Obama said Monday no decision had been made on whether to send weapons to Ukraine to help Kiev battle pro-Russian separatists, as he warned the West would not allow Russia to redraw Europe's borders by force.

Obama, who has faced increasing calls from domestic critics to supply the outmatched Ukrainian army with more weapons to shore up its faltering defenses, said he was still mulling his options.

German Chancellor Angela Merkel was Monday to brief U.S. President Barack Obama on the latest peace plan for Ukraine ahead of a four-way summit aimed at ending 10 months of bloodshed.

Foreign ministry officials from Ukraine, Russia, Germany and France were due to hold a preparatory meeting in Berlin after leaders agreed to push for the key meeting on a new peace deal Wednesday in Minsk, the capital of Belarus.

The United States is reportedly reconsidering a decision to invite Israel to a conference expected to be held in Washington next week after Lebanon decided to boycott it over claims that it cannot take part in a meeting to confront terrorism with the Jewish state's participation.

According to As Safir newspaper published on Monday, Lebanon's decision created a fuss among European countries that began wondering about the matter, which caused Washington to hesitate in its invitation.

The United States has invited the leaders of China and Japan for prestigious state visits, President Barack Obama's top security adviser said Friday, signaling a deepening of his "pivot to Asia."

"In furtherance of our relationships throughout this vital region, I'm pleased to announce today that we have invited Prime Minister (Shinzo) Abe of Japan and President Xi Jinping of China for state visits," said National Security Adviser Susan Rice.

Washington received an official apology from Lebanon on its participation in the “White House conference on efforts to counter violent extremism,” because it cannot be a “partner with Israel in confronting terrorism,” media reports said.

More than 60 countries, including 14 Arab nations and Israel, are expected to take part in the summit slated on February 18 at the White House and presided by U.S. President Barack Obama.

President Barack Obama believes the United States must resist the temptation to "over-reach" in its foreign policy and have "strategic patience" when it comes to tough international problems.

In a strategy document released Friday, Obama made the case for a more deliberative, cautious and restrained U.S. foreign policy. 

China is opposed to foreign countries receiving the Dalai Lama, a government spokesman said Friday, one day after U.S. President Barack Obama held a symbolic first public encounter with the exiled Tibetan spiritual leader.

"We are against foreign countries interfering in China's domestic affairs under the pretext of Tibet-related issues", Chinese foreign ministry spokesman Hong Lei told reporters.