WASHINGTON (AFP) – A new poll published on Wednesday found nearly half of Americans were opposed to US military involvement in Libya, reflecting tricky political ground being navigated by President Barack Obama.

But the Quinnipiac University survey also found that most voters were confident the US mission to shield civilians from Moamer Kadhafi could succeed, though there was an undercurrent of concern about a long engagement.

Qunnipiac also uncovered warning signs for Obama over his wider political prospects, with its survey recording its lowest-ever approval rating for the president -- 42 percent -- down from 46 percent earlier this month.

Respondents also said by a margin of 50 to 41 percent that Obama did not deserve to be re-elected in 2012.

"Some reasons for his overall numbers might be that Obama receives negative ratings on his handling of the budget deficit, the economy, foreign policy, health care and energy policy," said Peter Brown, the university's assistant director of polling

Other recent polls, most taken before the escalation of the US military effort in Libya, show Obama's approval rating between 48 and 51 percent.

More surveys will be watched in the coming days to see whether Obama's handling of the Libya crisis has hurt his popularity and dented his overall approval ratings.

The Quinnipiac survey was completed on Monday evening, as Obama made a major televised address to the American people to defend his Libya strategy against criticism that it lacked focus and a clear end-game.

Though it did not record reaction to his speech, the poll did reveal clear anxieties in public opinion about the Libya operation.

Voters polled opposed America's involvement in Libya by 47 to 41 percent.

However, 62 percent of voters were very or somewhat confident the mission to protect Libyan civilians would succeed.

But with the memories of the prolonged conflicts in Iraq and Afghanistan still fresh, 74 percent of voters were very or somewhat concerned that the United States will get stuck in a long-term military conflict in Libya.

Voters were closely split 46 to 45 percent on whether protecting Libyan civilians was worth have US troops fight and possibly die. But 61 percent thought that an operation to remove Kadhafi was not worth possible American combat deaths.

Obama has said that from this week, US air forces will play a mainly support role in air operations over Libya and insisted that he will not deploy US ground troops.

The survey was conducted between March 22 and March 28 and carries a margin of error of plus or minus 2.2 percentage points.