Check out the companies making headlines before the bell:

Berkshire Hathaway – Berkshire Chairman and CEO Warren Buffett told CNBC there is no truth to reports of tensions with 3G Capital, its ownership partner at Kraft Heinz. The reports were centered around the underperformance and accounting problems at the food producer.

Allergan – AbbVie announced a deal to buy its rival drugmaker for $63 billion, excluding assumed debt, or $188.24 per share in cash and stock. That represents a 45% premium over Allergan's Monday closing price. When debt is included, the deal is worth $83 billion.

Lennar – The home builder earned $1.30 per share for its second quarter, beating the consensus estimate of $1.14 a share. Revenue also came in above forecasts, although new orders were up just 1% from a year ago, while deliveries were up by 5%.

FactSet – The financial information provider reported adjusted quarterly profit of $2.62 per share, 25 cents a share above estimate. Revenue was also above forecasts. FactSet gave a full-year earnings forecast above current consensus, and also announced an increase of $210 million in its existing share repurchase program.

Tesla – Tesla was granted a waiver on 10% tariffs on aluminum imported from Japan, according to government documents seen by Reuters. The aluminum is used to make battery cells.

FedEx – FedEx sued the U.S. government over the White House ban on exports to certain Chinese companies, saying it was not reasonable to be expected to police the contents of millions of packages that it ships each day.

Amazon.com – Amazon announced that this year's "Prime Day" will actually take place for 48 hours over two days, July 15-16.

GrubHub – GrubHub was upgraded to "buy/high risk" from "neutral" at Citi, which is upbeat on the restaurant delivery service's growth trends and thinks it may be in early testing stages with large chains like McDonald's and Starbucks. Separately, the New York Post reports that GrubHub repaid an unnamed New York City restaurant more than $10,000 after a complaint about allegedly invalid fees.

Tiffany – The luxury goods retailer was downgraded to "hold" from "buy" at Loop Capital Markets, which points to weak tourist traffic and difficulty in achieving comparable sales targets.

MetLife – MetLife is in advanced talks to sell its Hong Kong insurance unit to insurer FWD Group, according to a Bloomberg report. The value of the unit is said to be less than $400 million.

Alphabet – A number of rivals are gearing up to help U.S. officials with an antitrust probe of the Google parent, according to The Wall Street Journal. Among them: TripAdvisor and Yelp, which have accused Google of favoring its own content in search results.