WASHINGTON — Lawmakers from the left-flank of President Barack Obama's Democratic party pressed him Thursday to combat high unemployment with "large-scale programs" including infrastructure spending.

"With 14 million Americans still looking for work, this is not the time to tinker around the edges. We must take bold action," Democratic Representatives Raul Grijalva and Keith Ellison urged Obama in a letter.

Grijalva and Ellison, who lead the House Progressive Caucus, said the embattled president should embrace that approach in his September 8 speech to a rare joint session of the US Congress.

"We encourage you to include in that package large-scale programs that will significantly reduce unemployment and our deficit," they said, urging "significant emergency jobs legislation to put Americans back to work now."

The lawmakers called for the creation of a national infrastrucutre development bank to oversee what they said was needed investments of some $2.2 trillion to repair crumbling roads and bridges.

"We should not delay these crucial investments, especially while millions of Americans are out of work. Rebuilding America -- without creating expensive new corporate tax loopholes -- will further boost our economy and create badly needed jobs," they said.

Obama's speech will likely open a new rift with House Republicans who refuse to accept new spending proposals and tax rises and want steep cuts in expenditures in programs dear to Democrats.

The plan is expected to consist of a mix of old and new proposals, including a call for tax rises on the richest Americans, more spending on job-creating infrastructure projects and an extension to a payroll tax cut.