President Barack Obama told his Afghan counterpart Hamid Karzai on Tuesday he is now planning a full U.S. troop withdrawal, but did not rule out agreeing a post-2014 mission with the next Kabul government.

The U.S. threat was the latest twist in a long political tug-of-war with Karzai, who has infuriated Washington with his refusal to sign a Bilateral Security Agreement (BSA) governing a post-2014 mission in the dying months of his mandate.

President Barack Obama Monday approved a civilian nuclear pact with Vietnam which could lead to the sale of U.S. reactors to Washington's energy-hungry former war foe.

The move by the president formally opened a 90-day review process in Congress. If no legislation is passed contravening the accord, it will then come into force.

Venezuelan President Nicolas Maduro urged Barack Obama to "accept the challenge" and hold direct talks, a surprise overture made Friday after days of accusing Washington of plotting his overthrow.

The announcement came after nearly three weeks of often violent anti-government protests in Caracas and other major cities, the biggest test to Maduro since he succeeded leftist icon Hugo Chavez last year.

China on Saturday accused the United States of meddling in its domestic affairs after President Barack Obama met the Dalai Lama at the White House, and said it is up to Washington to take steps to avoid further damaging ties.

"The U.S. seriously interfered in China's internal affairs by allowing the Dalai's visit to the United States and arranging the meetings with U.S. leaders," Chinese foreign ministry spokesman Qin Gang said in a statement.

U.S. President Barack Obama on Friday offered his "strong support" for the protection of Tibetans' human rights in China as he defied protests from Beijing to meet the Dalai Lama.

With China warning that the meeting would derail ties between the world's two largest economies, Obama took care to avoid any trappings of an official visit, receiving the exiled Tibetan spiritual leader in the Map Room of the White House residence and not the Oval Office where he usually talks to dignitaries.

The Arab Summit that will be held in Kuwait on March 25 and 26 is expected to tackle the latest developments in Lebanon and will be preceded by a meeting for the International Support Group for Lebanon that is set to be held in Paris in early March.

A diplomatic source said in comments published in As Safir newspaper that the Arab Summit will address the situation in Lebanon and stress its keenness to safeguard the country's stability, security and reiterate its support to the state's dissociation policy.

German Chancellor Angela Merkel and U.S. President Barack Obama joined with Russian President Vladimir Putin on Thursday to call for an urgent political solution to the deadly crisis gripping Ukraine.

"The chancellor and the presidents have reached an agreement to call for a political solution to the crisis in Ukraine as quickly as possible and for an end to the bloodbath," the German government said in a statement released after phone calls between the Western leaders and Putin, who have been at odds over Ukraine's future.

The United States has imposed visa bans on about 20 senior Ukrainian officials accused of backing the deadly repression of protesters in Kiev, a U.S. diplomat said Wednesday.

The move came in response to violent pitch battles that killed 26 people on Tuesday amid apocalyptic scenes that left parts of Kiev's historic city center engulfed in flames.

U.S. President Barack Obama urged Venezuela Wednesday to release protesters detained in anti-government demonstrations that turned violent and address the "legitimate grievances" of its people.

Obama condemned violence that has marred two weeks of protests in the oil-rich country against the leftist government of President Nicolas Maduro, with four people killed so far.

U.S. President Barack Obama on Wednesday warned of "consequences" over the violence in Ukraine and said it held the government responsible for ensuring that its people can protest "without fear of repression."

"We hold the Ukrainian government primarily responsible for making sure that it is dealing with peaceful protesters in an appropriate way, that the Ukrainian people are able to assemble and speak freely about their interests without fear of repression," Obama said during a visit to Mexico.