Nine-year-old Anna focused intently as she screwed a circuit board into place in a first-ever "DefCon Kids village" created to tutor children in the ways of hacking.

Her 10-year-old brother, Jake, was working on a similar task and beginning to suspect that the screws he was using were refusing to cooperate.

U.S. President Barack Obama on Saturday hailed the "extraordinary sacrifices" made by the 31 U.S. soldiers killed in Afghanistan when, according to local officials, the Taliban shot down their helicopter.

Obama also paid tribute to the seven Afghan soldiers killed during an anti-Taliban operation late Friday when a rocket fired by the insurgents struck their Chinook helicopter in Wardak province, southwest of the capital Kabul.

Italy pledged on Friday to work swiftly for a constitutional amendment requiring the government to balance its budget, as Rome feverishly tried to assure domestic and foreign investors its finances are sound and calm nervous markets in Europe.

Premier Silvio Berlusconi told a hastily convened evening news conference the government will "speed up measures" in its budget law approved last month by Parliament, "with the possibility of reaching a balanced budget by 2013 instead of 2014" as first planned.

The Obama administration sent its ambassador back to Damascus on Thursday as it incrementally turned up the heat on Syrian President Bashar Assad with tougher rhetoric and new sanctions.

The White House said Assad's deadly crackdown on protesters had put Syria and the Middle East on a "very dangerous path," as Washington extended a raft of recent sanctions to include a businessman close to Assad and his family.

The United States warned Thursday that President Bashar al-Assad had put Syria and the Middle East on a "very dangerous path," again toughening rhetoric on a crackdown by Damascus.

Washington appears to be moving towards a first direct call for Assad to go, a step it has so far resisted, and is preparing a new round of sanctions against his regime after an escalation of violence in the revolt hub of Hama.

The United States Wednesday said it had no interest in seeing Syria's President Bashar al-Assad survive simply to preserve regional "stability," hardening its line on what it termed a "grotesque" crackdown on dissent.

Some analysts have speculated that Washington has been wary of directly calling for Assad to quit because of anxiety that security chaos, civil war and a Middle East power vacuum might follow the demise of his regime.

A homeless man jumped the White House fence Tuesday triggering a security alert, but was quickly stopped by the U.S. Secret Service and arrested.

Two agents swiftly approached the man with their rifles drawn at him as he lay face down on the North Lawn of the White House.

The dollar climbed against the yen in Asia on Monday, after U.S. President Barack Obama announced an 11th-hour agreement to raise the U.S. debt limit to avoid default that is pending approval by Congress.

The dollar was at 77.45 yen in Tokyo at 05:00 GMT after briefly rising above the 78 yen level, from 76.73 yen in New York late Friday.

Tawhid movement leader Wiam Wahhab brushed aside on Friday a decision by U.S. President Barak Obama to extend a 2007 freeze of assets against him.

The decision is “meaningless,” Wahhab told Voice of Lebanon radio station (100.5), saying “it didn’t affect me in 2007 and won’t affect me today.”

Global stock markets fell on Monday amid growing concern about a potential U.S. default if lawmakers fail to agree a crucial deficit-cutting budget, dealers said.

Investor sentiment was also shaken after Moody's ratings agency sharply downgraded Greek debt -- and warned that the Eurozone rescue was almost certain to trigger another one-notch cut to default status.