* "Red shirt" supporters of PM rally at anti-graft commission
* Yingluck does not attend, sends legal team instead
* U.S., U.N., EU call for restraint as four-month crisis worsens (Adds protest leader proposing television debate with PM)
By Amy Sawitta Lefevre and Chaiwat Subprasom
BANGKOK, Feb 27 (Reuters) - Thailand's anti-corruption agency brings charges of negligence against Prime Minister Yingluck Shinawatra on Thursday as anti-government protesters demand her ouster in a standoff marred by violence that shows no sign of coming to an end.
The charges relate to a disastrous rice subsidy scheme that paid farmers above the market price and has run out of funds, adding to the government's woes as farmers - normally the prime minister's biggest supporters - demand their money.
More than 300 government supporters gathered outside the National Anti-Corruption Commission (NACC) in north Bangkok where the charges were due to be brought, as riot police stood guard inside the three-storey complex.
Some of Yingluck's supporters threatened to seal off the grounds with cement in a symbolic show of resistance to the legal action against her.
The anti-government protesters elsewhere in the city, whose disruption of a general election this month has left Thailand in paralysis, want to topple Yingluck and erase the influence of her brother, ousted premier Thaksin Shinawatra, seen by many as the real power in the country.
Protest leader Suthep Thaugsuban said he was willing to appear in a live television debate with Yingluck after weeks of refusing any form of talks.
"Just tell me when and where," he told supporters. "Give us two chairs and a microphone and transmit it live on television so the people can see."
Yingluck gave a guarded response to the proposal.
"If I talk to Suthep, will they stop protesting and will we be able to hold elections?" she told reporters in the town of Chiang Mai in the north, a Thaksin stronghold.
A general election this month was disrupted by the protesters and is unlikely to be completed for many weeks.
The protesters want to set up a "people's council" of unspecified worthy people to spearhead political reform before new polls are held, hoping that will stop parties loyal to the self-exiled Thaksin winning.
They have been on Bangkok's streets since November and have blocked main intersections for weeks to press their case.
Intermittent bursts of gunfire and grenade blasts have become routine at night in the political conflict, which has taken a heavy toll on tourism in the capital, famous for its golden temples and racy bars.
Rock guitarist Eric Clapton has pulled out of a Bangkok concert scheduled for Sunday because of deteriorating security.
Yingluck was a no-show at the anti-corruption agency hearing, sending her legal team instead.
The agency is investigating at least 15 cases against Yingluck and her party members, ranging from allegations of corruption in water projects to moves to make the Senate a fully elected body, which a court ruled illegal.
It alleges Yingluck was negligent for not ending the rice subsidy programme which it says was riddled with corruption. If found guilty, she faces removal from office and a five-year ban from politics.
"If her legal team hears the charges against her, she has 15 days to present evidence and after that the NACC will deliberate the case further," Wittaya Arkompitak, deputy secretary of the anti-graft commission, told Reuters.
Yingluck has denied negligence and accused the agency of bias, noting that a rice corruption case involving the previous administration had made no progress after more than four years.
The protests have triggered violence in which 21 people have been killed and more than 700 wounded.
The United States and European Union called for restraint. U.N. Secretary-General Ban Ki-moon said he was ready to help find a solution.
The crisis pits the mainly middle-class and southern anti-government demonstrators, who are backed by the royalist establishment, against the largely rural supporters of Yingluck and Thaksin in the north and northeast.
Both sides have armed activists and some pro-government leaders have called for Thailand to be divided in two, along north-south political lines, prompting talk of a civil war.
"As of now, there is no clear sign that (civil war) will happen," national security chief Paradorn Pattanathabutr told Reuters.
"There are those who think differently and respect the law who can no longer tolerate this ... The government must do everything it can to avoid confrontation and to prevent each side setting up stages or rallies near each other."
The standoff also raises the question of whether the military will step in, as it has many times before, most recently in 2006 to remove Thaksin, although the army chief has ruled out intervention this time.
But it has stepped up its security presence in Bangkok after two nights of violence.
"We have increased security checkpoints and bases for our troops to 176 locations near protest sites and important state buildings ... to look after security for all sides including civilians, government officials and protesters," said Wara Bunyasit, commander of the 1st Division King's Guard. (Additional reporting by Aukkarapon Niyomyat, Pracha Hariraksapitak and Pairat Temphairojana; Writing by Nick Macfie; Editing by Alan Raybould and Robert Birsel)