As the Senate gets ready to debate the details of a broad U.S. immigration bill, a group of House of Representatives lawmakers is still struggling to write its own legislation, hung up in part over guest worker programs sought by businesses.

Programs allowing employers in high-tech, agriculture, construction and other industries to hire foreign workers were also a stumbling block for senators who introduced a separate immigration bill last month.

In the end, the four Republicans and four Democrats in the Senate “Gang of Eight” group incorporated into its bill a deal reached between the AFL-CIO labor organization and the Chamber of Commerce, the huge U.S. business lobby.

Immigration reform is Democratic President Barack Obama’s top domestic priority. Although the Senate is controlled by Democrats, the bill will need some Republican support to meet the minimum 60-vote threshold for passage.

Still, passage of the bill in the Republican-led House is seen as the biggest challenge.