NEW YORK, June 20 (Reuters) - A rise in mortgage applications and a drop in jobless claims helped propel a gauge of the U.S. economy slightly higher last week, but the index's growth rate reached a four-year high, a report showed on Friday.

The Economic Cycle Research Institute, a private forecasting body, said its weekly leading index inched up to 123.4 in the week to June 13 from 123.2 in the prior week.

"The pervasive rise in the index reveals that the outlook for growth continues to improve, except in manufacturing," said Lakshman Achuthan, managing director of ECRI.

The index's growth rate, a four-week moving average that evens out weekly fluctuations, climbed to 6.1 percent from 5.5 percent in the prior week, a four-year high.

"With consumers as the main driver of recovery, growth is likely to remain subpar," Lakshman told Reuters.

The weekly leading index is composed of seven major economic indicators. ECRI designs short- and long-term indexes aimed at predicting business cycles, recessions and recoveries in the world's leading economies.