European leaders started tough negotiations over a proposed 80 billion euros ($103 billion) budget cut from 2014 to 2020 in Brussels on Thursday, triggering strong opposition from some member states and even staff members at European institutions.

It is expected that the negotiations may last through the weekend to achieve consensus. European Council President Herman Van Rompuy said they must reach a deal to shake off the debt crisis.

The proposal has received strong opposition. Sources said trade unions under European institutions planned to arrange a strike against the budget cuts on Wednesday, but it was canceled. Some skipped work on Wednesday to protest administrative cuts by European institutions.