Sharif Shehadeh told The Associated Press that the troops will have no effect on the ground, but that Washington wants to say it is present in Syria.
"What has happened to make America realize, after five years, that it should send between 30 and 50 military advisers?" asked Shehadeh, referring to the start of the country's crisis in March 2011 that has since killed more than 250,000 people.
American officials say up to 50 special operations troops will be sent to assist Kurdish and Arab forces in northern Syria.
The decision to send US troops to Syria comes a month after Russia began launching airstrikes against insurgents in the country.
Also Read
Russia's airstrikes were agreed upon with the Syrian government.
"When America sends ground forces into Syrian territories without an agreement with the Syrian government it becomes an intervention and aggression," Shehadeh said by telephone.
"Will America allow Russian ground forces to go into America without an agreement? I think the answer is no."
The US has conducted special operations raids in Syria before and is expected to continue to carry out more unilateral raids.
Earlier this month, US cargo planes dropped small arms and ammunition to Arab groups fighting IS in northern Syria in what appeared to be preparation for the attack.
Today, the Democratic Forces of Syria, a coalition of Arab, Christian and Kurdish factions in northern Syria, declared that they have started an operation to "liberate" areas south of the northeastern city of Hassekeh.
IS has several strongholds in the predominantly Kurdish province of Hassakeh that borders Iraq.