While the debate over the compromise tax agreement proposed by President Barack Obama has focused mostly on Bush's income tax cuts and whether they ought to be extended to wealthy Americans, the issue of estate taxes has also become a sticking point for some legislators.

Under the plan, the estate tax rate would be set at 35 percent, with an effective exemption of $5 million.

Many Republicans had hoped to do away with the estate tax altogether, and Democrats last year had proposed a higher rate: 45 percent on the value of estates over $3.5 million.