June 30 (Reuters) - The Standard & Poor's 500 and Nasdaq Composite indexes ended the second quarter of the year with their biggest quarterly gains since 2020, amid continued investor optimism about economic growth and earnings growth despite the Middle East war.

Both indexes ended the session higher on Tuesday, with the technology sector being among the top performers on the S&P 500.

Stocks have recently received a boost from optimism about signs of progress in efforts to end the war with Iran permanently, despite continued military tensions.

Iran and the United States signed a memorandum of understanding on June 17 aimed at ending the four-month-long war. But the weekend's exchange of fire puts that agreement at risk, and a Qatari official said on Tuesday that senior US envoys who arrived in Doha would not hold a high-level meeting with Iran.

"The first half of the year was great, and certainly better than most people expected," said Oliver Burch, senior vice president and advisor at Wealthspear Advisors in Westport, Connecticut.

He added, "Despite all the geopolitical developments, the US economy is performing well and corporate profits are strong."

Following a strong first-quarter earnings season for companies listed on the S&P 500, investors are looking ahead to second-quarter results in the coming weeks.

Preliminary data showed the S&P 500 closing up 55.97 points, or 0.75 percent, at 7,498.38, and the Nasdaq Composite gained 374.62 points, or 1.45 percent, to 26,194.76. The Dow Jones Industrial Average advanced 116.17 points, or 0.22 percent, to 52,298.91.

The weakness of shares in major technology companies has negatively impacted the market over the past few weeks.

Analysts at Bank of America said that cyclical sectors focused on value, such as energy and financial services, may be the best bet in the second half of the year.