WASHINGTON — Top Senate Democrats have prepared a plan to slice the Pentagon’s budget by $3 billion a year in an attempt to avoid far steeper cuts that defense hawks warn would cripple the military.

Majority leader Harry Reid, Democrat of Nevada, hopes to stage a vote before $85 billion in automatic budget cuts start to take effect in March. The bill is expected to produce about $120 billion in deficit savings over the coming decade, enough to block the automatic cuts through the end of 2013.