WASHINGTON, Oct. 10 (Xinhua) -- Seventeen years into war in Afghanistan, Americans remain pessimistic about U.S. involvement in the war-torn country, according to a recent survey by research center Pew.

About 49 percent of the U.S. adults say the United States has "mostly failed" to achieve its goals, according to the report released on Pew's website last week.

The poll also showed that about 35 percent of respondents said it has mostly succeeded.

In surveys conducted in 2014 and 2015, opinions about the mission were similarly more negative than positive, said Pew.

The Washington-based research center also revealed that between 2009 and 2011, when asked whether the United States will succeed or fail to achieve its goals, majorities said the United States would be successful.

Meanwhile, fewer Americans feel confident today that it was a right decision to use military force in Afghanistan. The poll showed that 45 percent of people say it's a right decision, down sharply from 69 percent in 2006.

Pew also noticed that Republicans have consistently expressed more support than Democrats for the decision to use force in Afghanistan, though support has fallen in both parties over the past decade.

The United States waged a "war on terror" in Afghanistan not long after the 9/11 attacks in 2001.