A US court has cleared the way for organic retailer Whole Foods Market to take over rival Wild Oats.
Whole Foods owns stores across the US, Canada and Southern England
The federal appeals court denied a request by the Federal Trade Commission (FTC) to block the $565m (£276m) deal.
The FTC had called for the deal to be blocked, saying it would stifle competition and lead to higher prices in the organic food sector.
Whole Foods contends that it needs to merge with Wild Oats to better compete against larger non-organic retailers.
Whole Foods' offer expires at the close of business on Monday.
The watchdog went to the US appeals court last week after a lower court judge refused to temporarily halt the merger.
In a 93-page ruling, US District Court Judge Paul Friedman rejected the FTC's claims that the deal would hurt competition and consumers.
The merger has hit the headlines in recent months after Whole Foods boss John Mackey made a number of controversial remarks about the deal.
Earlier this month he told his board of directors that bid target Wild Oats was the only rival that could give a traditional retailer access to the organic sector.
The claims came just weeks after he was forced to apologise about comments he made about Wild Oats - under a pseudonym on a Yahoo message board.
The posts, made under the name Rahodeb between 1999 and 2006, in part praised Wild Oats, but also claimed it was overvalued and poorly run.
Finance watchdogs are now investigating the posts, and Whole Foods has begun an independent inquiry.
Texas-based Whole Foods runs almost 200 stores across the US and the UK while Colorado-based Wild Oats has almost 110 outlets.