WASHINGTON (AP) ― A dispute over budget cuts that threaten dozens of smaller control towers with closure slowed Senate progress Tuesday on legislation to avoid a government shutdown on March 27.

Sen. Jerry Moran, R-Kansas, refused repeatedly to permit final passage of the measure unless Democrats first allow a vote on his plan for erasing most of the cuts aimed at towers operated by Federal Aviation Administration contract employees.

Senate Majority Leader Harry Reid, D-Nevada, just as persistently declined to give in, and other Democrats noted that House Republicans had rejected calls to give all federal agencies the type of budget flexibility that Moran was seeking.

The test of wills endured as Republicans and Democrats in Congress struggled with two goals ― ensuring there is no interruption of routine government funding while simultaneously vying for political advantage in the wake of $85 billion in across-the-board spending cuts that kicked in earlier this month.

Across the Capitol, the Republican-controlled House began debate on a budget that promises to eliminate federal deficits in decade. The blueprint, authored by Rep. Paul Ryan, D-Wisconsin, calls for $6.4 trillion in spending cuts and no tax increases, and is expected to clear by week’s end.

For their part, Senate Republicans kept their distance from the plan, deciding not to seek a symbolic vote on it when the Senate begins its own budget debate later in the week.

Sensing an opportunity for political mischief, Senate Democrats vowed not to let Republicans off easy. They said they would require a vote on Ryan’s budget ― even though they unanimously oppose it.

As gridlock gripped the Senate, the top U.S. commander in South America told Congress the cuts would reduce if not eliminate the entire fleet of ships used to counter drug-runners.

Gen. John Kelly said that U.S. forces seized 150 to 200 tons of cocaine last year. If the budget cuts stand, “next year all of that will make its way ashore and into the United States,” he told the Senate Armed Services Committee.

In the Senate, Moran said, “It’s not my nature to be an obstructionist” as he pressed his case. He added that his proposal has support from senators in both parties and that House Republican leaders have indicated the bill’s final approval would not be jeopardized if the change were incorporated.