WASHINGTON — As China presses ahead with a series of robotic lunar missions, its plans to begin a Mars exploration program could be delayed, a leading Chinese space scientist said March 31.

In a presentation at the National Research Council’s Space Science Week meeting here, Wu Ji, director general of the National Space Science Center of the Chinese Academy of Sciences, said that the Chinese government had yet to formally approve a proposal for a robotic Mars mission tentatively scheduled for 2020.

“We are aiming at 2020, but still we don’t have the green light from the government” to proceed with the mission, Wu said. He said that ongoing government reforms were at the root of the delays, which he said put the schedule of the mission in question. “There’s nobody really in charge to accept this proposal.”

Wu said feasibility studies for the mission are in progress by his academy as well as in industry. The current concept, he says, includes both an orbiter and a lander, the latter carrying a rover. He did not provide any technical details of the spacecraft, or planned scientific objectives of the mission.

This concept, if eventually approved, will not be China’s first attempt to send a spacecraft to Mars. In 2011, the Yinghuo-1 spacecraft launched as a secondary payload on Russia’s Phobos-Grunt mission. Yinghuo-1 would have gone into orbit around Mars while Phobos-Grunt attempted to collect a sample from the martian moon Phobos for return to Earth.

Phobos-Grunt, though, suffered technical problems after launch and never left Earth orbit, dooming Yinghuo-1. Wu said that experience, and the later success of India’s Mars Orbiter Mission spacecraft, led China to refocus its Mars exploration efforts on the orbiter and rover concept it is now pursuing.

While China’s Mars exploration program struggles to get underway, its lunar missions remains on schedule. Wu said China’s next lunar mission, Chang’e-5, is under development for launch in 2017 or 2018. That spacecraft will land on the moon and collect 200 grams of samples for return to Earth.

China tested some of the key systems for Chang’e-5 with a technology demonstration mission flown in October 2014. That flight included the successful test of a sample return capsule that re-entered Earth’s atmosphere at nearly 11 kilometers per second, versus 7.8 kilometers per second for capsules re-entering from Earth orbit.

That mission’s service module is still in lunar orbit performing rendezvous and docking tests, Wu said. “It was a very successful mission,” he said.

China is moving ahead with the sample return mission after the experience of its first lunar lander mission, Chang’e-3, which landed on the moon in December 2013. Despite technical problems with instruments on the lander, and mechanical problems that caused the lander’s small rover, Yutu, to stop moving about a month after landing, Wu said that mission was still viewed as a success.

Wu said that China had planned a second, similar lunar lander mission, called Chang’e-4, as a backup to Chang’e-3. With the success of Chang’e-3, however, China has postponed plans for Chang’e-4. “Because Chang’e-3 was so successful, the Chinese space agency doesn’t want to launch Chang’e-4 anymore” because there was little that could be learned from it, he said.

Instead, China now plans to fly an upgraded Chang’e-4 after the sample return mission. Wu said the revised Chang’e-4 mission, now scheduled for 2020, will use a more powerful launch vehicle that will allow for a heavier spacecraft and feature a landing in a different region of the moon, including possibly the far side.

Wu suggested that China would be open to international collaboration on instruments for that mission. “If you have good ideas and can provide instruments, you’re welcome to join Chang’e-4,” he said.

In addition to its moon and Mars missions, Wu said China is working on several concepts for space science missions. One, called the Magnetosphere-Ionosphere-Thermosphere Coupling Exploration Mission, would place several spacecraft in Earth orbit to study the interaction of the upper atmosphere with magnetic storms. That mission could launch in 2019 if selected in the next year as part of the next five-year plan.

Another mission, called the Solar Probe Orbit Telescope, or SPORT, would place a 1.2-ton spacecraft into an inclined, elliptical orbit around the sun. That mission could also be included in China’s next five-year plan, Wu said, although it is unlikely to fly until after 2020.