* Q1 production at 21.9 mmboe, up from 14.1 mmboe a year ago
* Says in line with 2013 production forecast of 88-94 mmboe
* Q1 production down 10 percent from the prior quarter
* Woodside shares slip around 3.5 percent
SYDNEY, April 18 (Reuters) - Woodside Petroleum Ltd , Australia's top oil and gas company, reported a 55 percent rise in first-quarter production on Thursday, boosted by its flagship Pluto liquefied natural gas (LNG) project.
The A$14.9 billion Pluto LNG project, which began production in April last year, is Australia's third gas-export project and the first to come online in six years.
It, alongside Angola LNG, is the only new supply due to enter the market until 2014 or 2015.
Woodside said its first-quarter production of 21.9 million barrels of oil equivalent (mmboe), up from 14.1 mmboe a year ago, was in line with its 2013 production forecast of 88 mmboe to 94 mmboe.
However, production in the three months to March 31 was down 10 percent from the prior quarter, due to an extreme cyclone season and the suspension of production at its Vincent oilfield for planned shipyard maintenance.
Quarterly sales revenue fell 18 percent to $1.45 billion.
Woodside's shares slipped around 3.5 percent to A$33.86 per share on Thursday afternoon, its biggest daily percentage drop since May last year.
Woodside also said it had held "several engagements" in the quarter with the Australian and East Timorese government over its prospective Sunrise LNG plant in East Timor, a project that has been locked in a sometimes bitter dispute.
Woodside prefers a floating LNG plant, while East Timor prefers an onshore plant that will provide jobs for locals.
But the East Timorese government released a statement on Thursday calling into question Woodside's cost estimates for a floating LNG plant, suggesting the two parties may not be any closer to agreeing on a development option.
"Margins of error on early developer's estimates are typically very high ... land based LNG is a well established and proven alternative, allowing the cost risk to be more tightly bounded," the East Timorese government said in the statement, adding that floating LNG could be nearly twice as costly as a land-based option.
Woodside said it sees "a window of opportunity to reach agreement on the project during 2013".
"Woodside, the Sunrise Joint Venture, and the governments of Timor-Leste and Australia are aligned in their desire to develop the Greater Sunrise fields. Through ongoing dialogue, we believe there remains an opportunity to agree on a development which satisfies the key requirements of all parties," the company said in an emailed statement.
Woodside said last week it had shelved plans for its $45 billion Browse LNG project in Western Australia, saying it will consider a floating LNG plant after deciding the onshore development did not make economic sense.
It said on Thursday that alternative development concepts will be evaluated.