* Honda, Mazda target around 10 pct sales rise in 2015
* Overall sales down 18 pct in H1
* Consumers delaying purchases as economy deteriorates (Updates auto sales data to H1)
By Fransiska Nangoy and Cindy Silviana
JAKARTA, July 14 (Reuters) - Japanese automakers are sticking to their targets in Indonesia in defiance of the longest sales decline in six years, resorting to steep discounts to entice tight-spending consumers into showrooms that remain stubbornly empty.
Honda Motor Co Ltd, Nissan Motor Co Ltd and Mazda Motor Corp aim to sell more cars this year than last, though overall sales to distributors have fallen each month since September and are down 18 percent in 2015.
"The decline is pretty drastic," said dealership salesman Jonatan, whose monthly average sales of Toyota Motor Corp cars was four versus eight last year. "We certainly have to work extra hard to sell cars these days."
Auto sales are a key indicator of consumption in Indonesia, where the economy is growing at its slowest since 2009, and where 7 percent inflation is eroding purchasing power. Consumers are consequently reserving more money for primary needs, the central bank said last month.
In response, automotive industry association Gaikindo in June lowered its sales forecast for this year to a range of 1 million to 1.1 million vehicles from 1.2 million.
"We are struggling with the market slowdown," said PT Honda Prospect Motor director Jonfis Fandy.
The firm has been trying to boost sales since early in the year via promotions usually reserved for Indonesia's annual automotive exhibition in August, to meet Honda's target sales increase of 10 percent.
Promotions include discounts on down payments, low-interest loans, and extending instalment periods to seven years from around four. Honda has sold 1.4 percent more cars as of end-May.
At Mazda, which aims to sell 9 percent more cars, one customer said he was offered 11 percent off a 450 million rupiah ($33,860.05) sports utility vehicle. But the mid-30s communication manager still delayed purchase for six months as economic conditions made him worry about finances.
Astrid Ariani Wijaya, senior marketing manager at PT Mazda Motor Indonesia - for whom year-to-date sales figures are unavailable - said the slowdown is affecting all industries, not just auto.
"What we are doing is maintaining advertising consistency in mass media," she said. "Discounts would depend on the model, and each dealer has different stocks."
Inflation and a weak rupiah are keeping the benchmark interest rate high at 7.5 percent, so the central bank is trying to boost demand by easing the passenger car down payment requirement to 25 percent from 30 percent.
"Willingness to spend money on big purchases is not there," said BNI Securities analyst Thendra Crisnanda. "So I doubt the down payment easing will be a significant help."
Auto demand usually peaks before Indonesia's Lebaran holiday in mid-July as consumers buy cars to visit home towns, but this year it is far less than expected, Crisnanda said.
At Toyota, one dealership salesman said supplies had fallen for its most popular multi-purpose vehicle, the Avanza.
Rahmat Samulo, a director at PT Toyota Astra Motor, said the company is making supply-demand adjustments and that, "if the stock is enough, we are not going to add excessively."
Toyota has sold 25 percent fewer cars as of end-May. It declined to disclose its 2015 target, but said it aims to maintain its market share of around 33 percent.
Japan's top automaker opened its second local plant in 2013, will open an engine factory next year, and plans to invest further in the country. Despite the slowdown, investment plans are "still on track", an official at PT Toyota Motor Manufacturing Indonesia told Reuters.
At Nissan, where sales are down 22 percent, its two local factories are running at 40 percent capacity, and have inventory turnover of about two months versus less than one month "during good days", Trimegah Securities said in a June report.
PT Nissan Motor Indonesia president director Steve Ardianto did not comment on production. But he said the firm is offering variants of current models, adding dealerships and improving service to lift its 2015 share to 6 percent from 4.7 percent. ($1 = 13,290.0000 rupiah) (Editing by Christopher Cushing)