WASHINGTON — A group of 15 House members including Rep. Bill Posey demanded Thursday that NASA find a way to continue a rocket program that President Barack Obama has proposed for elimination.

The House members sent a letter to NASA Administrator Charles Bolden telling him to assemble experts from Kennedy, Johnson and Marshall space centers to develop a plan for government rockets to reach the International Space Station and beyond.

"I'm asking the president to do what he promised. Nothing more. Nothing less. Nothing else," said Posey, R-Rockledge, of Obama's campaign pledge to continue human spaceflight. "I don't think there's anybody in the world who thinks that low-Earth orbit exclusively is keeping America first in space."

Obama has proposed ending the Constellation program of returning people to the moon, which administration officials said was underfunded and unrealistic. Instead, Obama proposed boosting research at the space station and relying on commercial rockets to get there.

Obama scheduled a space summit for April 15 in Florida to discuss his goals with experts.

But lawmakers of both parties in the House and Senate opposed Obama's budget proposal, leading to doubts that the House would approve it. In their letter, the 15 lawmakers sought an answer from Bolden before the summit.

"We've got a full-court press on this to oppose what the administration is trying to do," said Rep. Gene Green, D-Texas. "I can't vote for it," he said of Obama's budget.