U.S. Senate Republicans unveiled a tax plan on Thursday that differed from the House of Representatives' version on several key fronts, including how they treat the corporate tax rate, the tax deduction for state and local taxes, and the estate tax.

Complicating a Republican push for the biggest overhaul of U.S. tax law since the 1980s, senators said that, like the House, they wanted to slash the corporate tax rate to 20 percent from 35 percent, but in 2019, not right away.

The House was set to vote on its measure next week after its tax-writing Ways and Means Committee approved the legislation on Thursday along party lines, with Democrats united in opposition.