CARACAS, Venezuela (Reuters) - Foes of Venezuelan President Hugo Chavez, fighting to sustain a month-long strike that has choked vital oil exports, said on Tuesday they would carry their protest campaign into the new year, including a possible march on the presidential palace.

The strike, now in its fifth week, has throttled oil output, gasoline supplies and crude shipments by the world's No. 5 oil exporter, pushing world prices near two-year highs. Venezuela supplies more than 13 percent of U.S. oil imports.

The shutdown has caused alarm abroad and turmoil in Venezuela by disrupting fuel and food deliveries over Christmas. But it has so far failed in its aim to force the leftist president to quit and call early elections.

Despite signs of frustration in the opposition ranks, leaders vowed to pile up the pressure against Chavez in January.

"We will keep up our actions ... the strike will go on," anti-Chavez union boss Carlos Ortega told local television, adding protesters would become bolder in the new year and might stage a march on the Miraflores presidential palace.

"Let's all go to Miraflores, what's the problem?" he said, but gave no date for the march.

Miraflores has been off-limits to protesters since a coup was triggered in April by a demonstration that ended with 19 people dead and more than 100 injured.

Both government and opposition blamed each other for the killings, which led to an uprising by more than 100 rebel military officers that ousted Chavez for 48 hours.

One of those dissident officers, who have been occupying an east Caracas square in a peaceful protest since late October, was detained by DISIP state security police on Monday.

But, following an appeal from his lawyers, a Caracas court ordered the immediate release on Tuesday of anti-Chavez National Guard Gen. Carlos Alfonso Martinez. The authorities offered no explanation for the general's overnight detention.

Foes of populist Chavez, a former paratrooper elected in 1998, accuse him of ruining the economy with leftist policies, stirring up social hatred with his revolutionary rhetoric and trying to drag the country toward Cuba-style communism. He says he has turned the tide against the strike.

He has sacked dissident oil executives, used troops to help restart idled tanker ships, wells and refineries and also imported gasoline from abroad for the first time in 40 years.

Ortega said other planned protests included one outside Caracas military headquarters, probably on Jan. 3.

STRIKE SAPS ECONOMY

Chavez and his ministers say a march on Miraflores, located in a downtown bastion of government support, would be a deliberate attempt to provoke confrontation and topple the president by force in a repeat of the April coup.

Followers and foes of the outspoken president, who held rival street demonstrations over Christmas, planned separate New Year's Eve celebrations in Caracas later on Tuesday.

The strike's month-long disruption to oil exports accounting for half of government revenues is draining the oil-reliant economy, which has already contracted sharply this year. Inflation and unemployment have also been rising fast.

The effects of the shutdown, and fears of the fiscal crunch it will cause in January, have sparked a rush of nervous buying of U.S. dollars by banks, companies and individuals seeking to protect their savings.

The Venezuelan bolivar shed 2.5 bolivars against the dollar Tuesday, closing the year at 1,399.50/1,403.00 bolivars. The currency, battered by a year of unrelenting political turmoil, has lost 46 percent of its value against the dollar in 2002.

Chavez says the opposition strikers who have crippled operations in the giant state oil firm PDVSA belong to a rich, resentful elite opposed to his self-styled "revolution."

He says his reforms, which include a nationalistic oil strategy, increased state intervention in the economy and cheap credits and land grants for the poor, are aimed at eliminating minority privileges and distributing oil wealth more fairly.

Foes say his offensive to regain control of PDVSA is part of a strategy to consolidate economic and political power.

The government has pledged to restore oil output back to a third of normal next week. But exports remain at a trickle and the PDVSA strikers say the industry is still mostly shut down.

The opposition hopes to hold a nonbinding referendum on Chavez's rule on Feb. 2 but he has said he will pay no attention no matter what the result. He is sticking to a date in August, halfway through his current term, when he says the constitution allows for a binding referendum on his mandate.