The biggest set of U.S. tax increases in a generation took a major step forward on Wednesday with approval by the House Ways and Means Committee of $2.1 trillion in new levies, mostly focused on corporations and the wealthy.

The vote largely along party lines—there were no Republican votes in favor—brings President Joe Biden's $4 trillion longer-term economic agenda one step closer to enactment. The tax package will help pay for the biggest expansion in social spending in decades, in a budget bill currently penciled in at $3.5 trillion.

While the committee agreed to key elements—including tax increases on businesses and the wealthy, an extension of refundable child tax credits, and a bevy of incentives for clean energy—differences remain with legislation being developed in the Senate. With slim majorities in both chambers, Democrats expect weeks of wrangling to smooth out the disputes.