"I have also spoken with former military and administration officials and with diplomats and foreign policy experts," he said.
"I do not believe a military strike is the right course of action at this time."
Manchin hopes discussions with the Assad regime and other parties over the next 45 days will convince Syrian leaders to make sure their chemical weapons are secure and then to eliminate them.
"Even Russia is encouraging the Assad regime" to give up its chemical weapons, Manchin said.
"During that 45-day period, the president and the administration will have to look at a long-term solution in Syria and encourage additional diplomacy. ... I hope the White House will see this as a viable option."
Manchin also expressed concerns about a branch of al-Qaeda "participating with the rebels to oust the Assad regime. ... If they are successful in defeating Assad's regime, I believe al-Qaeda will have influence in the new regime.
"There is no doubt in my mind that the [chemical weapons] attack occurred and the weapons were produced under the Assad regime and that some part of the Assad regime was involved," Manchin said. "But there is no clear evidence that Assad gave the order [to use chemical weapons] himself."
By Friday, Manchin said, he had received or held more than 4,000 messages and conversations. "Less than 50 of them had any type of support for this type of attack."
A military attack on Syria, Manchin warned, "could cause more collateral damage and kill more civilians than what we have ever seen in the past.
"I want to see the civil war come to an end," Manchin said. "But I don't think we can stop the civil war by ourselves. But we have to get a hold of the chemical weapons. If we have a strike, that will not happen."
Manchin asked, "After 12 years of fighting and $2 trillion supporting military efforts [in the Middle East], what makes you believe we could continue that formula and have a different outcome?"
Reach Paul J. Nyden at pjny...@wvgazette.com or 304-348-5164.