From Washington,this is VOA News.

Peace talks between rebels in South Sudan and the government appeared to have stalled late Wednesday, with rebels saying there will be no truce until President Salva Kiir reverses himself and frees 11 jailed pro-rebel leaders.

So far, President Kiir has refused to release the detainees, who were arrested last year for their alleged roles in a coup plot.  Earlier in the day, government delegates said they were ready to sign a truce "soon," but they did not elaborate.

The two sides are meeting face-to-face for the first time in Addis Ababa, as fierce battles rage in their nearby homeland.

The White House and Republican leaders are speaking out in response to a new book, by former U.S. secretary of defense Robert Gates, that provides unflattering insights on the president, vice president and former secretary of state Hillary Clinton.

In "Duty: Memoirs of a Secretary at War," Gates describes the president as skeptical of his administration's "surge" strategy in Afghanistan.

White House spokesman Jay Carney responded Wednesday by saying Gates was an important part of a robust team whose opinions were needed to implement a "far improved policy in Afghanistan."

"When you pick a team of rivals, you do so, in part, because you expect competing points of view and competing opinions. And that's very much what the president expects in foreign policy and domestic policy and that's what he gets. And he's grateful for it."

In excerpts from the book, Gates criticizes the president for having a White House that was, in Gates's words, "the most centralizing and controlling in national security as any I have seen since Richard Nixon."

Gates was a Republican holdover from the George W. Bush administration and served for two years under Mr. Obama.

The United States is raising the pressure on Afghanistan's leader Hamid Karzai to sign a bilateral security agreement that would permit more than 8,000 U.S. troops to stay beyond the end of the year.As VOA Pentagon correspondent Luis Ramirez reports, the U.S. is again threatening a full withdrawal if Karzai does not sign the deal.

Militants capturing cities in Iraq is something U.S. officials don't want to see happen in Afghanistan.

The international troops that have helped Afghan forces fight extremists are due to withdraw in just 11 months.

Mr Karzai wants to wait until after Afghanistan's April elections before making a decision.  

U.S. officials say the longer the Afghan leader waits to sign the deal, the harder it will be for them and NATO allies to commit support.

Defense Secretary Chuck Hagel,"If you just look at our military and what we have to do in order to plan and prepare for a post-2014 mission train, assist, advise, counterterrorism, budgets, the Congress. This is complicated."

The U.S. military has tons of equipment and thousands of personnel to move in a short amount of time, but officials say they are setting no deadlines.

Luis Ramirez VOA News at the Pentagon.

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Russia has again blocked a United Nations Security Council resolution condemning Syrian airstrikes on rebels and civilians.

Wednesday's British-sponsored draft expressed outrage at the missiles and barrel bombs dropped on the besieged city of Aleppo since last month. The attacks have killed at least 700 people and wounded thousands.

Diplomats say Russia wanted to add amendments to the resolution which they say would have made it meaningless.

Russia - a strong Syrian ally - and China have blocked other resolutions condemning the Syrian government. But Russia backed moves that forced Syria to give up its chemical weapons. It is also co-sponsoring with the United States this month's peace talks in Geneva.

Earlier Wednesday, Syrian activists say rebels in Aleppo seized control of a hospital that had been used as a base by their al-Qaida-linked rivals.

The U.S. space agency NASA says it will keep the International Space Station operating for an additional four years, until 2024.

The $100 billion orbital station has been in service for 15 years, and the National Aeronautics and Space Administration had been planning to keep it running until 2020.

Separately, NASA said Wednesday that a scheduled supply flight to the space station on Thursday is in doubt, due to possible effects on communications of a strong storm on the surface of the sun that will send billions of tons of highly charged particles through the solar system this week.

VOA News.