U.S. stocks posted gains for the fourth straight session on Tuesday, as investors were encouraged by the Iran nuclear deal while digesting economic data and the second-quarter earnings reports from big companies.

The Dow Jones Industrial Average added 75.90 points, or 0.42 percent, to 18,053.58. The S&P 500 increased 9.35 points, or 0.45 percent, to 2,108.95. The Nasdaq Composite Index advanced 33.38 points, or 0.66 percent, to 5,104.89.

A landmark agreement has been reached over the Iranian nuclear issue between Iran and six world major countries, a diplomatic source confirmed Tuesday.

The comprehensive deal would be sent to the UN Security Council in a short time and it needs to be endorsed by the Council, and the period before the comprehensive deal starts to be implemented by all sides could be around half a year, the source said.

Meanwhile, a draft bill containing prior actions Greece needs to take under the debt deal reached in Brussels on Monday has been tabled in the Greek parliament, according to an official announcement by the Finance Ministry on Tuesday.

The bill which includes a first set of mainly taxation and pension system reforms was scheduled to be put to vote on Wednesday evening.

On the economic front, U.S. retail sales came out weaker than expected. Advance estimates of U.S. retail and food services sales for June were 442 billion U.S. dollars, a decrease of 0.3 percent from the previous month, missing market consensus of a 0.3-percent gain, the Commerce Department announced Tuesday.

"Spending momentum clearly stalled at quarter end, suggesting this year's Q2 bounce didn't have nearly the oomph of last year's, " said Chris Low, chief economist at FTN Financial, in a note.

The reporting season for major U.S. banks kicked off Tuesday. JPMorgan Chase & Co. rose 1.40 percent to 69.04 dollars apiece after reporting better-than-expected quarterly earnings. The bank earned 1.54 dollars per share for the second quarter of 2015 on a revenue of 24.5 billion dollars for the period.

Wells Fargo & Company reported net income of 5.7 billion dollars, or 1.03 dollars per diluted common share, for the second quarter 2015, compared with 5.7 billion dollars, or 1.01 dollars per share, for the same period last year. Its shares increased 0. 90 percent to 57.25 dollars apiece.

Johnson & Johnson announced sales of 17.8 billion dollars for the second quarter of 2015, a decrease of 8.8 percent as compared to the second quarter of 2014. The pharmaceutical firm's shares fell 0.49 percent to 99.78 dollars apiece on Tuesday.

The CBOE Volatility Index, often referred to as Wall Street's fear gauge, fell 3.81 percent to end at 13.37 Tuesday.

In other markets, oil prices ticked up Tuesday after Iran reached a landmark nuclear agreement with the world powers.

The West Texas Intermediate for August delivery moved up 84 cents to settle at 53.04 dollars a barrel on the New York Mercantile Exchange, while Brent crude for August delivery increased 55 cents to close at 58.40 dollars a barrel on the London ICE Future Exchange.

The U.S. dollar fell against other major currencies Tuesday as the lower-than-expected retail sales data from the country dampened market sentiment for an interest-rate hike as early as September.

In late New York trading, the euro rose to 1.1009 dollars from 1.1003 dollars in the previous session, while the dollar bought 123.33 Japanese yen, lower than 123.43 yen of the previous session.

Gold futures on the COMEX division of the New York Mercantile Exchange fell Tuesday ahead of U.S. Federal Reserve Chairwoman Janet Yellen's testimony before Congress Wednesday.

The most active gold contract for August delivery lost 1.9 dollars, or 0.16 percent, to settle at 1,153.50 dollars per ounce.