UPDATE 3-Old war foes face off in tense El Salvador vote

* Leftist ex-rebels seek power, voting tight

* Migrant workers return from United States to vote

* Government party has been in power since 1989 (Adds polls close, results due Sunday night)

By Catherine Bremer

SAN SALVADOR, March 15 (Reuters) - Salvadorans voted on Sunday in a tight presidential election that pits a party founded by Marxist rebels against right-wing civil war foes who have governed since 1989.

Tens of thousands of Salvadoran immigrants in the United States flew home to vote in a tense race that has reopened wounds from the 1980-92 Cold War-era conflict.

Cars full of voters, dressed in their Sunday best or wearing party colors, clogged the capital San Salvador's chaotic streets as supporters of both parties honked horns and waved flags.

Opinion polls gave a slight lead to leftist Mauricio Funes, a former TV journalist running for the Farabundo Marti National Liberation Front, or FMLN, with ruling-party conservative Rodrigo Avila just behind.

"It's time for a change. We are tired of this government. It promises things, but there are always more poor than rich," said Reina Cano, 22, a trainee lawyer. "Funes will be different. He's always been straight and honest."

With tensions running high after street clashes in recent days between militants from left and right, Funes urged his supporters to stay calm when he arrived to cast his vote, wearing a dapper gray suit.

Polls closed at 5 p.m. (2300 GMT). The first, and possibly definitive, results were expected within several hours.

A tight result could spark protests after a campaign blighted by civil war-era barbs. "The propaganda has been very ugly ... Neither side is going to accept losing," Dora Acosta, 59, said

Picking a candidate with no involvement in its guerrilla past has given the FMLN its best chance yet of ousting the right-wing Nationalist Republican Alliance, or ARENA.

Many voters want to join a shift to the left in Latin America, but others are squeamish at the idea of handing power to a party schooled in Cuban-style socialism as an economic crisis bites.

"We are not going to deliver the country to communism, like in Venezuela and Nicaragua," said a woman decked out in ARENA's red, white and blue colors at a San Salvador polling station.

Ruling party candidate Avila, a former national police chief, was a sniper with a paramilitary unit that fought with the army and has admitted killing leftist rebels in the war, which left 75,000 people dead. He once expressed admiration for a death squad leader who founded ARENA.

With close ties to business, ARENA says it is qualified to handle an economic slowdown. In its 20 years in power it has built up big manufacturing and service sectors and adopted the U.S. dollar in a country that used to rely heavily on indigo and coffee exports.

MONEY FROM U.S.

About a quarter of Salvadorans live in the United States -- a close ally of a string of right-wing governments during and since the civil war -- and the tiny nation relies heavily on the money they send home.

The government says as many as 40,000 Salvadorans may have flown in from the United States to vote.

But remittances and U.S. demand for Salvadoran factory goods are waning with the recession.

Funes, who used to host political talk shows critical of ARENA governments, vows to crack down on corruption and tax evasion and use the funds to create jobs and ease poverty.

He pledges to soothe the blow from the global economic crisis with policies to help the poor, while seeking friendly ties with business leaders and Washington, the FMLN's old foe.

He says he is a pro-business moderate, but his running mate, Salvador Sanchez, is an FMLN hard-liner who could take policy to the left and align the country with leftist governments in Venezuela and Nicaragua.

"If Funes wins we'll go backward 20 years. We'll be totally in (Venezuelan President Hugo) Chavez's hands," said tourist operator Carlos Palomo, 36.

The FMLN has gained in recent congressional races as young voters grow angry at a lack of prospects.

Jobless college graduates end up working in factories for $5 a day. Living costs have soared in recent years, and the failure to make ends meet is feeding violent street gangs.

"I voted for (Funes) because the poor stick with the poor, because we want a change," said drinks vendor Carlos Crespin. (Additional reporting by Anahi Rama, and Alberto Barrera; Editing by Paul Simao)