Russian Foreign Minister Sergei Lavrov admitted Friday the crisis over Crimea was "a difficult situation" as he began 11th-hour talks with U.S. Secretary of State John Kerry in London.

With just two days to go until a referendum in the Ukrainian region that the West fears will lead to it being annexed by Russia, Lavrov said: "This is a difficult situation we are in. Many events have happened and a lot of time has been lost."

U.S. Vice President Joe Biden on Tuesday met Didier Burkhalter, leader of Switzerland and current head of the OSCE group that is seeking a leading role during Ukraine's political transition.

Biden held nine phone calls with ousted Ukrainian leader Viktor Yanukovych in recent weeks, seeking to quell political violence, and has emerged as the White House's top pointman on the issue.

The White House on Tuesday called on Egypt to free three Al-Jazeera television journalists who have been held for more than a month, reportedly in harsh conditions.

President Barack Obama's spokesman Jay Carney said the detention of the journalists was "of deep concern" to the U.S. administration.

The White House called for an immediate end Sunday to clashes between security forces and protesters in Ukraine, warning of possible sanctions.

"We are deeply concerned by the violence taking place today on the streets of Kiev and urge all sides to immediately de-escalate the situation," National Security Council spokeswoman Caitlin Hayden said in a statement.

The United States welcomed the start of the Special Tribunal for Lebanon’s trial for four Hizbullah members accused of the Feb. 2005 assassination of ex-Premier Rafik Hariri.

“We have strongly supported the Tribunal’s efforts to hold accountable those responsible for destabilizing acts of violence in Lebanon,” White House spokesman Jay Carney said in a statement on Thursday.

President Barack Obama will meet Pope Francis "in the near future," the White House said Tuesday, although it did not specify a date for their much-anticipated first encounter.

White House spokesman Jay Carney said the president "looks forward" to the meeting with the pontiff, of whom he has spoken with admiration.

The U.S. Supreme Court appeared to be preparing Monday to limit the president's power to appoint high-level judges and officials while Congress is in recess.

By law, the president has the right to choose the nominees and lawmakers have the right to offer "advice and consent."

A White House-picked panel Wednesday recommended curbing the secretive powers of the National Security Agency (NSA), warning that its mass spying sweeps in the war on terror had gone too far.

The report said the NSA should halt the mass storage of domestic phone records, and called for new scrutiny on snooping on world leaders plus privacy safeguards for foreigners and fresh transparency over U.S. eavesdropping.

The White House Wednesday tried to quell a row with India over the arrest and strip searching of one of its female diplomats in New York, which sparked a fierce backlash.

White House spokesman Jay Carney said that Washington understood why the issue was such a sensitive one in India, where there has been public outrage, but said the incident did not reflect the broad and healthy cooperation between the two countries.

A review panel handed President Barack Obama a report Friday on surveillance by U.S. spy agencies in the wake of explosive revelations on vast phone and Internet sweeps by fugitive Edward Snowden.

The report contains more than 40 recommendations the White House will consider, and Obama will make a speech after a full-scale internal review of U.S. eavesdropping activity concludes in January, National Security Council spokeswoman Caitlin Hayden said.