House Republicans have whipped through a series of bills to crack down on illegal immigration with hopes they might provide an election boost in November.

But there's wide disagreement on what they would cost and little inclination among lawmakers to come up with the money in any case.

The House has passed and the Senate is debating legislation to build 700 miles of fence on the U.S.-Mexico border with no certain idea of how much it would cost.

Estimates range from $2 billion, cited by Sen. Judd Gregg, R-N.H., chairman of the appropriations subcommittee for homeland security, to $7 billion, the figure used by Senate Minority Leader Harry Reid, D-Nev.

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Homeland Security officials told congressional aides it would cost about $5 billion. The department would not confirm that figure nor address the cost of the 107 miles of fencing already up along the nearly 2,000-mile border. The cost can vary depending on whether the government or a private contractor builds the fence.

"We're trying to figure out how much it will be, but we have been funding it," House Speaker Dennis Hastert, R-Ill., said last week.

In a vivid demonstration of how hard it is to come up with the money, Hastert played to the cameras at a news conference by slapping red check marks on a placard to show border security accomplishments by House Republicans.

He left two items unchecked: funding for Border Patrol agents and for a Homeland Security contract for a high-tech border fence called the Secure Border Initiative.

The Senate put $1.8 billion in a Pentagon bill for 370 miles of fence plus another 500 miles of vehicle barriers. But they shifted the amount to a homeland security bill, where some of the money will pay for additional Border Patrol agents and jail space for immigrants awaiting deportation.

"We need to make sure we don't have a shell game," said Sen. Jeff Sessions, R-Ala., who is sponsoring the money for the fencing.

Senate Majority Leader Bill Frist, R-Tenn., said that because a 700-mile fence can't be built in a year Congress can provide just some money for it next year and the rest in the future.

Lawmakers, however, repeatedly have passed legislation ordering increases in border security without the money to pay for them.

The 2004 intelligence bill Congress passed called for doubling the number of Border Patrol agents by hiring 2,000 new ones each year for the next five years. It also authorized building or expanding detention centers for illegal immigrants by 8,000 beds a year during the period.

So far, however, Congress has put up enough money to pay for only 2,500 of the agents that were supposed to have been hired by next September, and only half of the 16,000 new detention center beds called for by then.

Sens. John Cornyn, R-Texas, and John Kyl, R-Ariz., tried to get $3.9 billion to pay for authorized projects or those sought by President Bush, but got nowhere. Left unfunded were new Coast Guard vessels and aircraft and a program for employers to verify that new hires are legally in the U.S.

A recent national survey found it will cost states $11 billion to implement a new federal law tightening rules on driver's licenses to prevent illegal immigrants from getting them. Congress is supposed to pay for some of it, but so far has come up with only $6 million for pilot programs.

"It's clearly a case of over promising," Cornyn said. "There's two steps. One is the authorization and the other is the appropriation and if appropriations don't follow, then it doesn't get done and that's been our track record."

Democrats say Republicans have rejected their seven attempts to increase border security funding since the Sept. 11 terrorist attacks. They contend there would now be 6,600 more Border Patrol agents, 14,000 more detention beds and 2,700 more immigration and customs agents if they had succeeded.

Rep. Solomon Ortiz, D-Texas, charged that when the House passed three more immigration bills last week, Republicans were just "blowing more hot air at voters who are angry that we say we're doing things to improve our border security."

"We never pay for them," said Ortiz, whose district includes the southernmost border with Mexico. "On the border, our not funding our promises brings local law enforcement a very large bill — yet another unfunded mandate."

The House and Senate are trying this week — before Congress recesses for the Nov. 7 elections — to send Bush a homeland security bill with more border protection money, including for agents, detention beds and security projects.

Neither of the measures meets the targets of some already enacted laws. For example, the House would pay for 1,200 new Border Patrol agents, the Senate 1,000. Both are short of the 1,500 that would have to be hired to comply with the promise two years ago of 4,000 new agents by next September.

"We've done a lot, but we haven't done all we need to do," Cornyn said. "We need to quit taking small baby steps."