COLOMBO (Reuters) -- Sri Lanka's cease-fire has given the Tamil Tiger rebels a chance to strengthen militarily, the island's defense minister said on Wednesday, but added that was the price of pursuing peace to end two decades of ethnic war.

But Tilak Marapana also rejected opposition claims that government forces were not ready in case the truce signed with the Liberation Tigers of Tamil Eelam (LTTE) in February last year breaks down.

"It is true that with the cease-fire ... many opportunities have been afforded to the LTTE to strengthen themselves," he told Parliament during a security debate.

"But that I believe is the price we have to pay if we are to pursue the peace process (as) a permanent solution of the problem," Marapana said.

The opposition and President Chandrika Kumaratunga, who is elected separately and is a political rival of Prime Minister Ranil Wickremesinghe, have repeatedly accused the government of ignoring what they said was an LTTE military buildup.

"The current neglect of the security forces and the steep decline of the preparedness of the military is alarming," Kumaratunga wrote in a letter sent to the prime minister earlier this month.

But Marapana said the military was aware of what the Tigers were doing.

"We have the plans, we have the troops and we have the equipment if the need arises," he said.

Security concerns have been raised because the Tigers have increased their number of fighters and set up additional camps in the east of the island.

But so far there have been no serious threats to the cease-fire since it was signed 19 months ago, the longest break in fighting after four previous truces ended in renewed bloodshed.

The Tigers are preparing a response to a government proposal on power-sharing in the north and east, which should be ready in the next several weeks.

Direct talks, which the LTTE walked away from in April, are expected to start after that, although there is no date.