US stocks traded flat on Tuesday as yields on Spain's 10-year bond hit a euro-era high, pointing to continued stress in the nation's debt markets shortly after an announced European Union bailout.

While a $125 billion aid package to Spain did ease some concerns about the region's debt crisis, questions remained about the terms of the deal and the impact it could have on Spanish debt levels.

US equities have been closely correlated to developments in Europe's financial crisis on concerns about how it might impact global growth prospects.

Investors also looked to critical weekend elections in Greece, which are still viewed as a major headwind that could result in the country leaving the euro zone.

Nicholas Colas, chief market strategist at the ConvergEx Group in New York, predicted swings in equities around the close of European markets, “since that's where all our catalysts are coming from.

“It is nice to see us holding above 1,300 (on the S&P), which is an important number psychologically, but it is very possible that we see another disappointing sell-off like yesterday,” he added.

Volatility after the close of European markets is expected to persist until more clarity is received on Greece's government makeup and the stability of Spain's banking system.

The Dow Jones industrial average was up 18.47 points, or 0.15 percent, at 12,429.70. The Standard & Poor's 500 Index was down 0.60 points, or 0.05 percent, at 1,308.33.

The Nasdaq Composite Index was down 2.75 points, or 0.10 percent, at 2,806.98.

On Monday, the first trading day after the Spain aid package was announced, shares rallied early in the session before steadily losing ground, ending 1 percent lower.

Energy and material shares, both of which are heavily tethered to sentiment about Europe, were the top gainers, with both up 0.5 percent. Among the most active, Valero Energy Corp rose 3.5 percent to $22.61 while Halliburton Inc was up 1.2 percent to $27.82. US Steel Corp rose 1.3 percent to $18.13.

Michael Kors Holdings Ltd rose 5.5 percent to $40.30 after posting stronger fourth-quarter profit growth and giving a strong full-year outlook.

May US import prices fell 1 percent from April, as expected, according to Labor Department data. Export prices fell 0.4 percent, compared with the expectation for a drop of 1 percent. - Reuters