WASHINGTON (Reuters) - President Barack Obama on Monday urged the Senate to approve legislation that would reveal who is behind election campaign advertising, and chided Republicans for opposing a measure he said would protect American democracy.

The Senate is due to vote on Tuesday on a bill that would blunt a Supreme Court ruling allowing unlimited campaign spending, against which Obama has been an outspoken critic.

“You’d think that reducing corporate, and even foreign influence over our elections would not be a partisan issue,” Obama said in Rose Garden remarks at the White House.

“But of course this is Washington in 2010, and the Republican leadership in the Senate is once again using every tactic and every maneuver they can to prevent the Disclose Act from even coming for an up or down vote,” he said.

The bill would force the disclosure of the sources of election advertising spending and ban financing from companies with more than 20 percent foreign ownership.

Republicans say it is designed to protect Democrats worried about their chances in the November 2 congressional elections.

“The Disclose Act seeks to protect unpopular Democrat politicians by silencing their critics,” Republican Senate leader Mitch McConnell said.

The January Supreme Court ruling overturned long-standing campaign finance limits and will allow companies to spend freely in elections. It is expected to unleash a wave of money before the November poll and the 2012 presidential race.

Obama said disclosing who is behind an election ad would serve an important role in policing campaign finance.

“A group can hide behind a name like ‘Citizens for a Better Future,’ even if the more accurate name ought be ‘Companies for Weaker Oversight,” he said. “These shadow groups are already forming and building warchests of tens of millions of dollars to influence the fall elections.”