Washington ? Engaging in partisan political warfare, President Bush and the Senate Democratic leader blamed each other Saturday for the Senate’s failure to pass legislation to overhaul immigration laws.

Bush used his weekly radio address to thrust himself into the thick of the immigration battle, accusing Senate Minority Leader Harry Reid of Nevada of obstructing the bipartisan compromise announced Thursday. Bush called on Reid to end his “blocking tactics” on the reform bill, which stalled Friday.

“We should … conduct the debate on immigration reform in a manner worthy of our nation’s best traditions,” Bush said. “To keep the promise of America, we must remain a welcoming society and also enforce the laws that make our freedom possible.”

Reid lashed back, accusing Bush of failing to provide the leadership necessary to overcome conservative Republicans’ antipathy toward the Senate compromise.

“It was President Bush and Republicans in Congress who lacked the backbone to stand up to the extreme right wing of their party,” Reid said in a statement.

The comments added to the increasingly partisan tone surrounding immigration reform, which has emerged as an important issue for both parties going into mid-term elections later this year.

Immigration advocates now fear that both Republicans and Democrats will use the debate over immigration to score political points, rather than seek a comprehensive reform this year.

Sisters Yvonne Barnes , left, and Nakita Doucet of Garland, Texas hold signs reading LEGAL

Several activists agreed on Saturday that Bush’s leadership over the coming weeks could prove key to the bill’s fortunes. The Senate is in recess for two weeks, and mass demonstrations are expected across the country on Monday.

Frank Sharry, the executive director of the National Immigration Forum, an advocacy group, said Bush needed to apply the full weight of the White House to ensure the compromise measure’s success.

Sharry said Bush’s endorsement of the Senate’s compromise could force House Republicans to toe the line and provide Senate Democrats with the assurances necessary to move the bill forward.

“The president is the key now,” said Sharry, whose group supported the Senate compromise. “It’s up to Bush to engage as strongly as the White House can to bring this thing across the finish line.”