The resignation of Kofi Annan, UN-Arab League joint special envoy on Syria, is unlikely to lead to a greater probability of direct Western military intervention, U.S. experts said Friday.

David Pollock, a senior fellow with the Washington Institute for Near East Policy, said Annan's stepping down, however, will likely lead to greater emphasis on U.S., European and Arab policy to support the opposition indirectly.

Some analysts believe that the U.S. reluctance to forcefully intervene in the Syrian crisis is mainly due to its fears that the security of Israel, a close ally of the country, could be endangered if extremist groups come to power in post-Assad Syria.

Earlier in the day, Syrian government troops blasted artillery at rebels in Aleppo, the country's commercial center and most populated city, where the United Nations said the army was preparing a massive assault.

Wayne White, a scholar at the Middle East Institute, noted that government forces have been fighting nonstop for some time and are slowly being ground down.

Government forces are doubtless exhausted and losing strength, White said, adding that equipment is likely beginning to wear under the stress of continued combats.

The Syrian government may be putting too many eggs in one basket in Aleppo, considering that other sections of the country are not completely under government control, he said.

Meanwhile, arms and large quantities of ammunition are falling into rebel hands as insurgents continue to take police station after police station. "This thing is now practically an all-out civil war," White said.

Annan, who assumed his current post about five months ago, announced in Geneva on Thursday that he would step down after his current mandate expires on Aug. 31, saying he was disappointed over the lack of progress in the Syrian peace process. E