MADRID, June 30 (Reuters) - U.S. President Joe Biden said on Thursday the United States supports the sale of F-16 fighter jets to Turkey and that he is confident the congressional approval needed for the sale can be obtained.

Speaking at a news conference in Madrid at the end of a NATO summit, he rejected suggestions that Washington's support for the sale was in return for Turkey lifting its block to the NATO membership of Sweden and Finland.

An 11th-hour deal struck on Tuesday between Turkey, Finland and Sweden after four hours of talks helped avert an impasse at the gathering of 30 NATO leaders that aimed to show resolve in the face of Russia's invasion of Ukraine.

"I said back in December, as you'll recall, we should sell them the F-16 jets and modernize those jets as well," he said. "It's not in our interest not to do that."

"And there was no quid pro quo with that. It was just that we should sell, but I need congressional approval to be able to do that. And I think we can get that."

Turkey made a request in October to the United States to buy 40 Lockheed Martin Corp-made (LMT.N) F-16 fighters and nearly 80 modernization kits for its existing warplanes.

Sentiment toward Turkey in the U.S. Congress has turned sour over the past few years after Ankara acquired Russian-made defense missile systems, triggering U.S. sanctions as well as Turkey's removal from the F-35 fighter jet program.

Turkish President Tayyip Erdogan told a news conference in Madrid said he believed Biden would make "sincere efforts" to ensure the support of U.S. Congress for the sale and that he would send a delegation of Turkish officials to the United States to help lobby for the deal.

The two leaders met on Wednesday on the sidelines of the NATO summit in Madrid.

On Wednesday, a senior Biden administration official also expressed support for the sale for the first time. Assistant secretary for defense Celeste Wallander told reporters that strong Turkish defense capabilities would reinforce NATO's defenses.