NEW YORK (TheStreet) -- Stock futures on Tuesday pointed to a slight extension of Monday's rally as hopes for a Greek debt deal continued to fuel positive investor sentiment.

S&P 500 futures were up 0.17%, Dow Jones Industrial Average climbed 0.11%, and Nasdaq futures added 0.2%.

"The downward revisions to April's estimates suggest that there was a much weaker start to investment activity this quarter and despite the small rebound in May's investment activity the contribution to GDP this quarter from investment activity will remain quite modest at best," said Millan Mulraine, deputy head of U.S. strategy at TD Securities. 

Stocks rose on Monday as the prospect of a Greek debt deal finally looked like a possibility. That helped the S&P 500 and Dow Jones Industrial Average to close with robust gains and the Nasdaq to notch a new record close. Click here for more.

Eurozone finance ministers reacted positively to new proposed reforms submitted by the Greek government in a meeting on Monday. Among the reforms reported, though not confirmed, Greece will eliminate early retirement benefits, cut defense spending and increase corporate tax rates. Eurozone leaders will meet again at the end of the week. Talks have escalated as Greece faces a crucial repayment to the International Monetary Fund by the end of the month.

BlackBerry (BBRY) shares added more than 5% in premarket trading despite missing analysts' quarterly estimates. The company posted a fiscal first-quarter loss of 5 cents a share, 2 cents narrower than expected, while revenue of $658 million dropped nearly 32% from a year earlier and missed estimates by more than $25 million. On the plus side, BlackBerry's transition to software over smartphones appeared to be proving successful. Software and technology licensing revenue rose 150% in the quarter to $137 million.

Darden Restaurants (DRI) added more than 6% on news the company will transfer 430 company-owned restaurants to a real estate investment trust.

Facebook (FB) is now worth more than Wal-Mart (WMT) just three years after going public. A surge in share price over the last year has added more than $65 billion to Facebook's market value to bring its total to more than $238 billion. Wal-Mart is worth $235 billion. Click here for more.

Syngenta (SYT) has made clear it will not entertain acquisition offers that undervalue the company. In a YouTube video, Syngenta Chairman Michel Demare said a "serious proposal" would need to be "made at full and fair value." Syngenta recently rejected a $45 billion offer from Monsanto (MON). 

Sonic (SONC) fell nearly 5% after reporting an in-line third quarter and weaker comparable-store sales. The restaurant chain reported same-store sales rose 6.1% in the third quarter, affected by harsh weather in some of its regional operations.  

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