Pre-Market Brief:

MARKET SNAP: At 5.46 a.m. ET, S&P 500 futures up 0.8%. Treasurys 0.01% higher at 1.99%. Nymex up at $107.38; gold advances to $1,702.2. In Europe, FTSE 100 up 1.1%, DAX gains 1.7% and CAC 40 rises 1.8%. In Asia, Nikkei 225 p 2% and Hang Seng increases 1.3%.

Overnight action: China blocks sales of Airbus jets;Greece moves close to swap; U.S. warns Apple, publishers.

Watch for: Jobless claims. Economists expect 353,000 after last week's 351,000 reading. Precursor to the monthly employment report, due tomorrow. Greece's debt exchange deadline on tap. Earnings expected from Aeropostale, Navistar and Zumiez, among others. For additional details, check this week's upcoming events.

The Breakfast Briefing

One and done? It's far too early to say whether it will last, but Wednesday's action and this morning's premarket moves are bringing some cheer to the bulls.

After suffering its first triple-digit decline of 2012 on Tuesday, the Dow Jones Industrial Average bounced back nicely the very next day, gaining 78.18 points, or 0.61%, to finish at 12837.33.

But after three months of steady gains, was Tuesday's 212-point slump enough to serve as the pause that refreshes this rally?

Not if Greece has anything to say about it.

Kathy Lien, director of global research and analysis at GFT, doesn't mince any words when she says: "Thursday is D-Day for the euro." And to some extent, that's the case for stocks, bonds, commodities and general global investor sentiment, too.

The focal point today will be the rate of voluntary participation by bondholders in a Greek sovereign bond swap. The range of outcomes is wide: If enough bondholders step up to swap 90% of the bonds, you can more or less take a credit event off the table; stocks and the euro will soar, and we'll see just how much Greek default fears have weighed on the recent market rally.

On the other hand, if the massive debt swap fails to attract 75% of the participants, we're much more likely to see a credit event declared; in that case, look out below. Anywhere in between, Ms. Lien says, is a bit of a gray zone.

The bond swap offer ends at 3:00 p.m. EST, so you can expect much of Thursday's U.S. trading to take place in the shadow of that deadline.

As of 5:30 a.m., reports suggested investors holding around 60% of eligible Greek government bonds have indicated they will participate in the debt swap.

European markets are up and Asian markets closed higher amid growing optimism the deal will get done. The positive sentiment is spilling into the action in U.S. stock futures, with Dow futures up 86 points and S&P 500 futures up 10 points, as of 5:30 a.m.

Also on tap: a European Central Bank monetary policy announcement, and more clues on U.S. unemployment, courtesy of the weekly initial jobless claims numbers -- set to hit the tape at 8:30 a.m.