Washington  - US President Barack Obama on Tuesday defended his ambitious budget proposals, which have been strongly resisted by conservatives, telling skeptics that his plans were in line with the enormity of the problems faced by the country's economy.

"The challenges we face are too large to ignore," Obama said after a meeting with members of the congressional budget committees.

Obama last month proposed a 3.5-trillion-dollar budget for 2010 that included large increases in spending on health, energy and education as well as more government funds to fix a financial crisis that has plunged the US into recession.

The budget, which also outlines his plans over the next 10 years, has already set off a firestorm of debate among legislators in Congress that could continue through September. Opposition Republicans have derided the plans as a dramatic expansion of government that does little to curb the federal deficit.

Obama pointed to his promise to cut the deficit in half by the end of his first term and defended investments in problems such as health care as critical for the economy's long-term health. He challenged his opponents to offer "constructive" alternatives over the next few months.

"With the magnitude of the challenges we face right now, what we need in Washington are not more political tactics, we need good ideas," Obama said.