(CNN) -- Syria's president on Sunday accused the United States of trying to destabilize Syria by providing political support to rebels fighting the regime.
Bashar al-Assad also said a months-old peace plan aimed at ending the violence has not failed, but it has yet to be implemented because countries are supporting the "terrorists" in Syria.
Al-Assad's interview with German broadcaster ARD aired as the opposition Local Coordination Committees of Syria reported another 60 people killed in the country Sunday.
It also came the same day U.S. Secretary of State Hillary Clinton said the Syrian regime's days are numbered. Noting a number of recent defections from the regime, Clinton said, "the sand is running out of the hourglass."
U.N. Secretary-General Ban Ki-moon added Sunday that the situation in Syria has deteriorated significantly and become more militarized. "Appalling" human rights violations continue, he said, and the killings and violence have turned even more sectarian.
"President Assad must understand that things cannot continue as they are. Fundamental change is needed," he said.
Al-Assad said in the interview it should not be those outside Syria who get to decide his future, telling ARD it should be up to the Syrian people.
"The people will decide who should be our representative, the people's representative, through the ballot box," he told ARD.
Former U.N. Secretary-General Kofi Annan, now the United Nations and Arab League joint special envoy to Syria, brokered a six-point peace plan in March. The Syrian government accepted the plan, which proposed an end to the violence, access to humanitarian groups, and an inclusive political dialogue.
"Kofi Annan is doing, so far, difficult but good work," al-Assad said. "There are many obstacles, but it shouldn't be a failed plan."
Annan arrived in Damascus on Sunday for talks with al-Assad, Annan's spokesman said.
Asked about Annan's plan for a unity government in Syria, al-Assad said one already exists, pointing to local elections in December in which opposition members won a small number of seats. That they didn't win more, he said, was down to the voters.
Al-Assad said the United States is "of course" implicated in the deaths of Syrian civilians as long as it provides political support to terrorists in the country.
The United States "is part of the conflict," he said. "They offered an umbrella -- political support -- to those gangs to create instability, to destabilize Syria."
The regime has long blamed the violence in Syria on terrorists, armed gangs, and foreign fighters bent on creating unrest. Al-Assad said Sunday that some of the captured terrorists hail from Tunisia and Libya.
The president said he welcomes a visit by Clinton or any other U.S. official to hold "serious and honest" discussions about its role in the country.
"We never closed the door," he said. "They closed the door."
While he said the United States is offering political support to the rebels, other countries are arming them. He named Saudi Arabia and Qatar, and said he doesn't have concrete evidence but goes by their foreign ministers' official announcements that they want to support the rebels with arms.
Al-Assad also said Turkey is "offering logistical support for smuggling" weapons. The state-run Syrian Arab News Agency reported Sunday that two "terrorists" had confessed to smuggling gunmen and various types of weapons from Turkey, and that one of them received weapons training from Turkish security forces.
SANA also reported Sunday that authorities foiled an attempt by an armed terrorist group to enter Syria from Turkey. Security forces killed and wounded a number of terrorists while the rest fled back to Turkey, it said.
Another group tried to cross the Turkish border into Syria on Friday, the news agency reported.
Al-Assad said it was "gangs" who carried out the massacre in May of more than 100 children, nearly half of them children, in the town of Houla. About reports that the perpetrators wore Syrian army uniforms, al-Assad said the gangs wore them to make the government look guilty.
That has been a strategy of the rebels "from the very beginning," he said.
The president said he has a two-pronged solution to ending the fighting, beginning with combating the terrorists.
"The other axis is to make dialogue with the different political components, and at the same time, we have reform," he said.
Asked whether this reform should be sped up, al-Assad said a timetable would be subjective. It's happening as quickly as possible, he said, but it must be based on circumstances inside the country.
The United Nations has said more than 10,000 people have been killed since the Syrian crisis began in March 2011. What started as peaceful protests against the regime spiraled into a bloody government crackdown and armed uprising.
One opposition group, the Syrian Observatory for Human Rights, said last week that more than 16,700 have been killed, including more than 11,000 civilians.
CNN cannot independently verify government and opposition claims of casualties because access to Syria by international journalists has been severely restricted.
CNN's Nunu Japaridze and Melissa Gray contributed to this report.