WASHINGTON – A bipartisan group of leading senators has reached agreement on the principles for a sweeping overhaul of the nation's immigration laws, including a path to citizenship for the 11 million illegal immigrants already in this country.

The deal, to be announced at a news conference Monday, also covers border security, non-citizen or "guest" workers and employer verification of immigration status.

Although thorny details remain to be negotiated and success is far from certain, the development heralds the start of what could be the most significant effort in years toward overhauling the nation's inefficient patchwork of immigration laws.