Syrian President Bashar al-Assad has warned of an "earthquake" if the West intervenes in his country.
In a rare interview with the UK's Sunday Telegraph newspaper, Mr Assad said involvement risked transforming Syria into "another Afghanistan".
The UN has renewed its call for the repression to end, and China has warned Syria the situation cannot continue.
More than 50 civilians and members of the security forces were killed on Saturday, according to the two sides.
Activists said 21 civilians were killed and that army tanks had shelled a historic district in the city of Homs.
The government said 20 soldiers were killed in Homs, and 10 members of the security forces were killed during an ambush of their bus in Idlib province.
More than 3,000 people have died in the unrest since protests calling for the government of Mr Assad to step down broke out in March.
In the Sunday Telegraph interview, Mr Assad said Western countries were "going to ratchet up the pressure, definitely".
"Syria is the hub now in this region. It is the faultline, and if you play with the ground you will cause an earthquake," he said.
"Any problem in Syria will burn the whole region. If the plan is to divide Syria, that is to divide the whole region.
"Do you want to see another Afghanistan, or tens of Afghanistans?"
President Assad admitted that "many mistakes" had been made by his security forces in the early part of the uprising, but the paper said he insisted that "only terrorists" were now being targeted.
He said he had responded differently to the Arab Spring than other, deposed Arab leaders.
"We didn't go down the road of stubborn government," he said. "Six days after [the protests began], I commenced reform."
Mr Assad described the uprising as a "struggle between Islamism and pan-Arabism".
"We've been fighting the Muslim Brotherhood since the 1950s and we are still fighting with them," he said.
Meanwhile China's Middle East envoy Wu Sike said he had warned Syria on his recent visit to Damascus about the "danger of the situation and that it cannot continue".
Mr Wu, now in Cairo, said he had told Mr Assad he must "respect and respond to the aspirations and rightful demands of the Syrian people".
UN Secretary-General Ban Ki-moon said Mr Assad must respond to demands for change with serious reform, "not repression and violence", and called for an immediate halt to military operations.
His calls echo those of members of the Arab League who on Friday sent an "urgent message" to the Syrian government, denouncing "the continued killings of civilians" taking part in protests.
The Arab League's ministerial committee on the Syrian crisis also urged Damascus to "take the necessary measures" to protect civilians.
League officials are meeting Syrian counterparts again in Qatar on Sunday to discuss the possibility of a dialogue between the Syrian government and the opposition.
However, the League's two-week deadline for such a dialogue to start expires on Sunday.
On Saturday, two of the country's main activist groups, the British-based Syrian Observatory for Human Rights and the Local Co-ordinating Committees, said shells had hit the Baba Amr district of Homs.
Reuters news agency reported that one person was shot dead by a sniper and two were killed during machinegun fire between Mr Assad's forces and defectors in the city. Activists said that 21 civilians had been killed on Saturday, including 12 in Hama and three in Homs.
Raids and arrests also were reported around the eastern city of Deir el-Zour, the Associated Press reports.
In another incident near Homs, up to 20 Syrian soldiers were killed and 53 wounded in clashes with presumed army deserters, according to Agence France-Presse.
In a separate incident, 10 security agents and a deserter were killed in a bus ambush near the Turkish border, AFP reported, quoting activists.
The Observatory said the bus was transporting security agents between the villages of al-Habit and Kafrnabuda in Idlib province when it was ambushed "by armed men, probably deserters".