Two Senate rebels jumped into Congress' cut-the-deficit competition on Tuesday, proposing to raise the age of Medicare eligibility to 67 and increase monthly premiums for millions of current beneficiaries.

"We can't save Medicare as we know it," said Sen. Joseph Lieberman, I-Conn., who authored the plan with Republican Sen. Tom Coburn of Oklahoma. "We can only save Medicare if we change it," he added in an apparent jab at President Barack Obama and congressional Democrats.

Democrats reacted with criticism of the proposal, which Coburn said was designed to rescue the financially imperiled program and help the nation confront a "wall of debt." Republicans betrayed no sign of support either.

If nothing else, the response underscored the difficulty of legislative free-lancing at a time the Obama administration and congressional leaders are struggling to negotiate a compromise that cuts future deficits and clears the way for an increase in the nation's $14.3 trillion debt.

Without a debt limit increase by Aug. 2, Treasury Secretary Timothy Geithner has warned, the government could default, risking calamity for the U.S. economy and serious effects worldwide.

Republicans walked out of bipartisan talks last week but nevertheless said negotiations had been fruitful. In the days since, Obama has stepped up his personal involvement in the effort.

Shareholders at refinery operators Frontier Oil Corp. and Holly Corp. voted on Tuesday to merge their companies, in a $3 billion deal expected to close Friday.

Frontier Oil said the deal was approved by 99 percent of the shareholder votes cast. The same percentage of Holly shareholders voted to issue the shares necessary for the share swap transaction, the company said. Holly shareholders also approved changing the company's name to HollyFrontier Corp., the surviving business once the merger closes.

The deal was announced in February as part of a wave of consolidation in the refining industry. Refineries that had struggled to pass on high oil prices during the recession started to see profits surge last year as demand grew for gasoline and other fuels. Marathon Oil announced earlier this year that it would spin off its refining business, and ConocoPhillips plans to minimize its refining arm from 24 percent to 15 percent of its core business.

Shaw Group Inc. said on Tuesday that problems with a subcontractor on an energy and chemicals project and troubles on another project triggered a $70 million loss in its fiscal third quarter.

Shares of the engineering and construction company dropped 12.6 percent in after-hours trading.

After markets closed, Shaw reported a loss of $70 million, or 89 cents per share, for the three months ended May 31. That compared with net income of $68.2 million, or 79 cents per share on more shares outstanding, in the same quarter a year ago.

Analysts surveyed by FactSet had forecast a profit of 68 cents, on average, in the latest quarter. Analysts' estimates typically exclude one-time items.

Revenue dropped nearly 17 percent to $1.49 billion from $1.79 billion in last year's fiscal third quarter.

Shaw said that unspecified "subcontractor execution issues" resulted in cost increases to the company on an energy and chemicals project. That reduced earnings by $112.8 million on a pretax basis, and $68.9 million after taxes.

The Baton Rouge-based company also recorded a pretax accounting impairment of $48.1 million, or $29.4 million after taxes, on loans made to Nuclear Innovation North America's South Texas Project.

A look at the 10 biggest volume decliners on New York Stock Exchange at the close of trading:

Blk DefOppCredTr : Approximately 7,500 shares changed hands, a 88.2 decrease from its 65-day average volume. The shares rose $.06 or .4 percent to $13.90.

Gabelli Hltc&Well : Approximately 10,300 shares changed hands, a 79.6 decrease from its 65-day average volume. The shares rose $.06 or .8 percent to $7.60.

Hubbell A : Approximately 200 shares changed hands, a 86.7 decrease from its 65-day average volume. The shares rose $.75 or 1.3 percent to $58.00.

Huntington Ingalls Industries Inc. : Approximately 160,000 shares changed hands, a 81.6 decrease from its 65-day average volume. The shares rose $.06 or .2 percent to $35.26.

Korea Fund Inc. : Approximately 1,400 shares changed hands, a 93.1 decrease from its 65-day average volume. The shares rose $.28 or .6 percent to $47.75.

Nuveen New York Select Tax Free Income Portfolio : Approximately 600 shares changed hands, a 86.4 decrease from its 65-day average volume. The shares rose $.10 or .7 percent to $13.53.

Primedia Inc. : Approximately 51,000 shares changed hands, a 81.9 decrease from its 65-day average volume. The shares rose $.01 or .1 percent to $7.10.