SEATTLE -

Political leaders are locked in lengthy negotiations this week as they try to develop a massive transportation package for Washington state.

After a five-hour-long negotiating session on Monday, lawmakers returned to Gov. Jay Inslee's office Tuesday to continue talks. Inslee is hoping that an agreement can be in place before the end of the year.

Lawmakers have been struggling all year to reach agreement on a transportation plan, which would likely rely on a large increase in the state gas tax.

The House and Senate have each offered varying proposals valued at roughly $10 billion. They differ on how to handle issues such as transit funding and how to handle money dedicated for cleanup projects.