House Speaker John Boehner told Republican colleagues Tuesday he is shifting to a \"Plan B,\" allowing tax breaks to expire for millionaires as a way to avoid the so-called fiscal cliff, his office said. Boehner will introduce legislation in coming days that keeps tax rates from rising on the vast majority of Americans, what his office called a \"second track\" of action amid negotiations between Boehner and President Barack Obama. \"Time is running short,\" Boehner\'s office quoted him as telling his caucus in a Tuesday morning meeting, referring to the year-end deadline to work out a deal or have $500 billion in taxes hikes and crippling spending cuts kick in. \"Taxes are going up on everyone on January 1. They\'re baked into current law,\" Boehner said. \"And we have to stop whatever tax rate increases we can. In the absence of an alternative, as of this morning, a \"modified Plan B\" is the plan.\" Obama on Monday offered Boehner his latest counter-proposal in a tortuous negotiating process now homing in on a January 1 deadline, offering a major compromise on the income level affected by his demand to raise taxes on the rich. The latest plan would raise the threshold at which higher rates would come into force to households earning $400,000 a year and above, up from the $250,000 level on which Obama had earlier insisted. Boehner has accepted higher taxes on people making more than $1 million. Obama\'s new proposal offers some $1.2 trillion in revenue hikes and an identical level in spending cuts designed to trim the deficit over the next decade, a source familiar with the plan said. The president had initially insisted in $1.6 trillion in higher revenue from raising taxes and then lowered the number to $1.4 trillion. Boehner has now reportedly offered $1 trillion in new revenues. Boehner is not stepping away from negotiations with the president. But his office has stated that despite a flurry of Obama-Boehner negotiations in recent days, including a face-to-face meeting Monday and a phone call later in that night, the White House has yet to offer a balanced deal. \"What the White House offered yesterday -- $1.3 trillion in revenue for only $850 billion in spending cuts -- cannot be considered balanced,\" Boehner said. \"We\'re going to keep the door open in hopes the president can find a way to support a balanced approach.\"