COLOMBO, Feb 4 (Reuters) - The United States and Britain urged a temporary ceasefire in Sri Lanka to evacuate casualties and allow relief into the war zone as the Island nation celebrates independence from colonial ruler Britain on Wednesday.

President Mahinda Rajapaksa was due to preside at a parade of military might in the capital on Wednesday morning that will include fighter jets flying overhead and attack boats sailing by to mark the 61st independence anniversary.

The military was on high alert as troops surround the rebel Liberation Tigers of Tamil Eelam (LTTE) in a 300-sq-km (115 sq- mile) slice of jungle in the Indian Ocean island's northeast, aiming to end a war that started in 1983.

A joint statement issued by the United States and the United Kingdom, following a meeting between Secretary of State Hillary Clinton and Foreign Secretary David Miliband, raised serious concerns about the plight of civilians in northern Sri Lanka.

"Secretary Clinton and Foreign Secretary Miliband call on both the Government of Sri Lanka and the LTTE to agree to a temporary no-fire period. Both sides need to allow civilians and wounded to leave the conflict area and to grant access for humanitarian agencies," the statement said.

The United States, European Union, Japan and Norway on Tuesday urged Tamil Tiger rebels to consider surrendering to avoid more deaths, including among thousands of civilians trapped in the war zone.

FLEEING HOSPITAL

The call for the separatist rebels to discuss a surrender came as the International Committee of the Red Cross (ICRC) said civilians were fleeing a hospital in the war zone that had been shelled for a fifth time in three days.

The ICRC says at least 12 people have been killed in the hospital in Puthukudiyiruppu.

Sri Lanka's military has encircled the Tigers and is confident it will end a conflict that has killed 70,000 people in one of Asia's longest-running insurgencies.

Sri Lankan President Mahinda Rajapaksa last week gave the Tigers 48 hours to free thousands of civilians trapped in the battle zone, which the LTTE ignored.

The government had promised safe passage for that time, but on Monday said it could not guarantee the safety of anyone still living among the rebels, unless they enter an army-demarcated no-fire zone.

Aid agencies say 250,000 people are trapped in Tiger-held areas, but the government says the number is about half of that. The military and the rebels again traded blame for the shelling.

It is nearly impossible to verify accounts from the war zone, off-limits for journalists except on carefully guided tours. (Reporting by Ranga Sirilal; Editing by Bill Tarrant)

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