With Japan’s Nikkei index posting its biggest one-day gain in more than three months, US equities opened higher on Monday and then extended those gains to new 2009 highs.

At 12:30, the S&P 500 is building on its 2.2% gain last week by trading 0.66% higher at 1,035. The Dow is up 0.61% to 9,564, and the Nasdaq is trailing with a 0.40% gain to 2028.

“Risk is back on amid optimism that the global economy is on the mend,”said Sal Guatieri from BMO Capital Markets.

Spurring the gains are a 3.1% advance for new orders to industrial companies in the euro zone. Markets were only expecting a 1.8% gain. Meanwhile, markets in Asia climbed in reaction Friday’s Existing Home Sales report in the US, which jumped 7.2%.

“The longest and deepest recession of the postwar era has ended, and a new global expansion is beginning in the third quarter,” declared economists at IHS Global Insight. 

In a client note sent out this morning, Global Insight projected that the world’s real GDP  would expand by 2.4% in 2010, after a projected 2.3% decline this year. For 2011, the forecasting firm looks for 3.4% growth.

“With housing and automotive markets turning around, the U.S. economy will resume growth this summer quarter, lending strength to the other Americas,” the note said. “European economies appear to be stabilizing, although banking problems, the bursting of real estate bubbles, and rigid labor markets will impede recoveries in countries such as Italy, Spain, and the United Kingdom.”

One caveat in their forecast is that “a sustained, robust global recovery” is dependent on “renewed growth in consumer spending and capital investment.” Sustained consumer spending could be tough sell as Americans shift towards greater savings, and retailers will have a tough job demanding full prices after months of heavy discounting.

No macroeconomic data has been or will be released today. However, some bad news about the expanding US deficit was published by Reuters: “An administration official told Reuters the 10-year budget deficit projection will jump by about $2 trillion to roughly $9 trillion from an original forecast of $7.1 trillion.”

The official report is to be published tomorrow by the White House budget office and the non-partisan Congressional Budget Office.

News from the weekend and a schedule from Tuesday to Friday can be seen in The Week Ahead.