WASHINGTON, Nov. 13 (Xinhua) -- The number of new international students enrolling at U.S. high education institutions fell by 6.6 percent during the 2017-18 academic year, on top of a 3.3 percent decline the year before, a report showed on Tuesday.

China remained the largest single source of international students, accounting for about a third of all students who came to the United States for postsecondary degrees, followed by India, South Korea, Saudi Arabia and Canada, said the report.

The 2018 Open Doors Report was released jointly by the Institute of International Education (IIE) and the U.S. Department of State's Bureau of Educational and Cultural Affairs.

The total number of international students in the United States surpassed 1 million for the third consecutive year, increasing by 1.5 percent to reach a new high of 1,094,792, the report showed.

China sent the most students in 2017 -- 363,341, marking a 3.6 percent enrollment hike, according to the report.

Current gains in the total number of international students studying in the United States are due primarily to increased participation in the Optional Practical Training (OPT) program, said the IIE in a press release.

The OPT program allows international students to practice their skills in the country for up to 12 months during or after they complete their academic programs, or up to 36 months for students who have earned a degree in STEM fields.

OPT participation grew by 15.8 percent in 2017/18. Among enrolled students, drops were seen primarily at the graduate and non-degree levels, according to the IIE.

As for U.S. students, the number grew by 2.3 percent to 332,727 Americans studying abroad for academic credit at their home institutions in 2016/17. Approximately one in 10 U.S. students study abroad during their undergraduate career.

Concerning the fall of new enrollment, some experts said the current political climate in the United States has made international students feel unwelcome, leading some to enroll elsewhere.

Others noticed that though the United States remains the top host of international students globally, it is losing students to other English-speaking countries such as Canada, Australia and Britain, which have all seen growth in the past year.

Allan Goodman, IIE president and chief executive, said that global competition for students is intensifying.

"We're not hearing that students feel they can't come here," Goodman said. "We're hearing that they have choices. We're hearing that there's competition from other countries, and that, in this very sophisticated, very competitive market for the first time, we have real competition."

International students made a significant financial impact on the United States, contributing 42.4 billion dollars to the U.S. economy in 2017 through tuition, room and board, and other expenses, according to the U.S. Department of Commerce.

"International students studying alongside Americans are a tremendous asset to the United States," said Marie Royce, Assistant Secretary of State for Educational and Cultural Affairs. "We want to send a message that international education makes us stronger as a country."