WASHINGTON, March 3 (Reuters) - Quickly ending U.S. reliance on Russian rocket engines could add up to $5 billion to the cost of upcoming satellite launches, Air Force Secretary Deborah James said on Thursday at a contentious Senate hearing where lawmakers raised several hot-button issues.

James said Air Force efforts to develop a U.S. rocket engine for powering heavy satellites into space were advancing, but an early ban on use of RD-180 rocket engines from Russia would force the service to choose other launch providers.

“Preliminary analysis suggests that a transition ... would add anywhere from $1.5 billion to $5 billion in additional costs...,” she told the Senate Armed Services Committee. “The sooner a full RD-180 ban might start, the more disruptive it would be ... and the higher the cost would be.”

Senator John McCain, chairman of the panel, is pushing legislation to end U.S. dependence on Russian engines used by United Launch Alliance to power its Atlas 5 rockets.

Congress passed a ban on the engines after Russia annexed Ukraine’s Crimean peninsula in 2014. But lawmakers weakened the restrictions last year out of concern they could force ULA, a joint venture of Lockheed Martin Corp and Boeing Co , out of business.

McCain said two Russians placed on the U.S. sanctions list because of events in Ukraine were leaders of Russian space agency Roscosmos, which he said was the parent company of the company that makes the RD-180 rocket.

“So we have now two sanctioned cronies of (Russian President) Vladimir Putin who are getting X millions of dollars of taxpayers’ money,” McCain said.

McCain and other lawmakers also raised questions about an Air Force proposal to delay retiring the popular A-10 “Warthog” ground support aircraft until 2019. Some lawmakers believe it should be kept in service until something else can replace it.

“We have a conflict going on in Iraq and Syria now ... which the A-10 is in combat in ... and you have nothing to replace it with,” McCain told General Mark Welsh, the Air Force chief of staff, himself a former A-10 pilot.

Welsh told lawmakers the problem was not with the A-10 but with spending cuts imposed by Congress.

“I find myself in a almost surreal position, arguing to divest things I don’t want to divest, to pay a bill we were handed in law,” Welsh said. “And we’re not being allowed to pay it by the institution that passed the law.” (Reporting by David Alexander)