Peru is going ahead with a $266 million upgrade of its fast aging combat aircraft while it considers how to keep its air force up to speed with changing technologies and modern warfare requirements.

Peru faces no external threat, but President Ollanta Humala is under increasing pressure to be more proactive in the government's crackdown on Shining Path guerrilla groups that caused a Cabinet crisis earlier this month with resignations by Defense Minister Alberto Otarola and Interior Minister Daniel Lozada.

The ministers were criticized for their handling of the aftermath of April kidnapping by the guerrillas of 36 construction workers in southeastern Peru. The workers were released but the security operations left nine members of the government forces dead.

In a country short of cash resources, the multimillion dollar spending on the reconditioning of old French Mirage jets and former Soviet MiG warplanes has raised eyebrows, but analysts explain the stopgap solution is the best the country can manage at present.

Critics say the government needs to do more to acquire weapons that can tackle the Shining Path threat.

The alternatives are a higher expenditure or a foreign loan. Amid global slowdown in military sales, Peru will have no trouble rearming its forces with credit from any of the suppliers desperate to boost their exports, but Humala is demonstrating prudence -- for now.

Both French and Russian suppliers have campaigned for boosting their defense aviation sales in Latin America. Other European and Asian suppliers have followed their lead and Brazil has joined the race with its competitively priced Super Tucano light attack aircraft -- no match for either Mirage or MiG but more suitable for the fight against the guerrilla groups.

Peruvian government officials are also considering unmanned aircraft for military duties but have not come to a decision.

Peruvian air force estimates say the upgrading of its Mirage 2000 and MIG-29 combat aircraft will entail an investment of $266 million, the Diario Correo newspaper reported.

Work on the upgrades is already in progress and its completion is scheduled for 2014, the newspaper said.

Peru began buying Mirages from France in 1986 and the current upgrade involves 12 aircraft. Although Mirage maker Dassault Aviation is helping with the upgrade, officials said the bulk of the work is being carried out by Peruvian engineers and aviation experts.

The upgrade of 18 MiG-29 aircraft however is not running as smoothly as anticipated because most of the work requires Russian expertise. The MiGs' refurbishment is likely to cost at least $126 million.

The upgrading programs began about six years ago under the presidency of Alejandro Toledo and a key part, training of the pilots in the uses of new technologies, is continuing with French help.