A small, bipartisan group of U.S. senators who crafted legislation on immigration reform are scheduled to begin daily meetings Tuesday to defend the proposal during two weeks of what is expected to be fierce debate in the full Senate.

The bill would give the estimated 12 million illegal immigrants in the United States a path to legal status. It would establish a temporary worker program, increase border security, and punish employers who knowingly hire illegal immigrants.

Some critics say the bill is not tough enough on illegal immigrants because it effectively gives them what they consider amnesty.

On the other side of the issue, some Hispanic groups have opposed the plan because it puts limits on family-based immigration.  They are also criticizing the temporary worker program, because it would require workers to return home for a year after each two-year work period.

The controversial bill was unveiled last week. Senate Majority leader Harry Reid had originally planned to hold a vote on it this week, but abandoned that plan after senators complained they needed more time to evaluate the proposal.

President Bush has made immigration reform a top priority. A White House spokesman said Tuesday that much criticism of the bill is based on misinformation.