Britain's economy is better but is "still stuffed to the eyeballs with toxic substances", warns a senior HSBC economist.
The Dow Jones closed higher at 10611.81, up 44.51 points (0.42%), marking its third day of rises and its highest closing level since January 19.
The Chancellor has signalled his next Budget will not be a "giveaway".
The FTSE was sharply down in afternoon trading at 5609.61, down 30.96 (0.55%), as mining woes and disappointing US weekly jobs figures pared back yesterday's gains.
South African banking group Investec will join the ranks of the largest companies in the London market when it replaces Resolution in the FTSE 100.
The Chancellor will use the Budget to hike capital gains and inheritance taxes to fund Gordon Brown's pledge today not to cut front-line services, Legal and General predicts.
The Prime Minister today pledges not to "let down" the people of Britain on the economy, but warns there is still danger ahead.
The FTSE 100 was up 11 this morning at 5,613 points, with financials peppering both sides of the gainers and losers tables.
Gordon Brown has confirmed 24 March as the day for the 2010 Budget ahead of a May General Election.
Tax hikes or spending cuts to the tune of an extra £20bn will be needed by 2013/14 to close the fiscal gap, according to PricewaterhouseCoopers.