July 5 (Reuters) - A survey published on Sunday showed that Saudi Arabia's non-oil private sector accelerated its growth in June, supported by the strongest rebound in new business volume in four months, although firms continued to struggle with severe cost pressures and weak external demand.

The seasonally adjusted Purchasing Managers’ Index (PMI) for Saudi Arabia, issued by Riyad Bank, rose to 53.3 in June from 52.8 in May, marking its highest reading in four months and indicating a strong improvement in operating conditions towards the end of the second quarter.

Output growth remained generally stable, with about 18 percent of surveyed firms reporting an increase in activity compared to only 2 percent that recorded declines.

Survey participants attributed this to the approval of new projects, increased customer demand, and the return of orders that had been previously postponed due to the conflict in the region.

New business volumes rose at the fastest pace since February, as easing geopolitical concerns boosted investor confidence and increased domestic spending.

Naif Al-Ghaith, chief economist at Riyad Bank, said, "The rise in production and the faster increase in new orders over four months indicate that business activity has regained momentum as the second quarter draws to a close."

However, not all indicators were positive. Export orders contracted sharply for the fourth consecutive month amid logistical hurdles and fierce foreign competition, while employment stagnated.

Meanwhile, input costs recorded their highest quarterly increase in 15 years, prompting companies to raise their product prices at the second-fastest rate in nearly six years.