(Adds Kerry comments, Moualem letter, background)
By Arshad Mohammed and Lesley Wroughton
WASHINGTON, Jan 16 (Reuters) - The United States urged Syria's opposition on Thursday to attend Jan. 22 peace talks and criticized its government for suggesting the meeting should be about fighting terrorism rather than forging a political settlement.
The comments by Secretary of State John Kerry, less than a week before the talks are to begin, suggest some uncertainty by the United States over whether the opposition will show up at the U.N.-hosted conference in Montreux, Switzerland.
The main umbrella opposition body in exile, the Syrian National Coalition, which is riven with internal divisions, will decide on Friday whether it will attend the conference. Syria's centrist internal opposition group, the National Coordination Body, on Thursday said it would not attend.
In a hastily arranged appearance, Kerry also faulted what he called "recent revisionism" about why the peace conference is being held after some three years of civil war in Syria in which more than 100,000 have died and millions have been uprooted.
Kerry said the talks, known informally as "Geneva II" although it is being held in Montreux, were to carry out a 2012 plan calling for a political settlement under which the two sides would together agree on a transitional government.
"For anyone seeking to rewrite this history or to muddy the waters, let me state one more time what Geneva II is about," Kerry said. "It is about establishing a process essential to the formation of a transition ... governing body with full executive powers established by mutual consent."
The United States has taken the position that "by mutual consent" means that Syrian President Bashar al-Assad cannot take part in any transitional government because his participation would be rejected by the opposition.
U.S. officials said Kerry was reacting to a letter from the Syrian government confirming its attendance at the meeting but saying that the government's focus was on fighting "terrorism."
The letter, from Syrian Foreign Minister Walid al-Moualem to U.N. Secretary-General Ban Ki-moon, also said the government did not accept all aspects of a U.N. letter inviting it to the peace conference.
A copy of the invitation sent to one of the parties and obtained by Reuters reiterated the goal of the two sides agreeing on a transitional ruling body with full executive powers as laid out in the 2012 "Geneva Communique."
"Confirmation of attendance will be taken as commitment to the aims of the conference ... in accordance with the Geneva Communique, in particular the principles and guidelines for a Syrian-led transition," the letter of invitation said.
"We do not agree with certain points mentioned in the letter, simply for the reason that they are in conflict with the legal and political position of the State of Syria; nor do they meet the supreme interests of the Syrian people," Moualem wrote.
"It remains as the priority to the Syrian people to continue to fight terrorism ... we also demand the countries supporting terrorism to cease and refrain from funding, training, arming or harboring terrorist groups," it added, in a dig at countries such as Saudi Arabia believed to be arming the Syrian rebels.
Syria sank into civil war after a peaceful street uprising against four decades of Assad family rule began in March 2011. The revolt spiraled into an armed insurgency after the army responded with massive and deadly force to suppress the unrest.
Without mentioning Moualem's letter specifically, Kerry put the blame for the violence on the Syrian government.
"The world needs no reminder that Syria has become the magnet for jihadists and extremists. It is the strongest magnet for terror of any place today," he said. "It defies logic to imagine that those whose brutality created this magnet ... could ever lead Syria away from extremism and toward a better future." (Additional reporting by Louis Charbonneau at the United Nations and Dominic Evans in Beirut; editing by Chizu Nomiyama and Cynthia Osterman)