(Reuters) - U.S. congressional negotiators are making progress on resolving a dispute that has stalled a bill to impose new sanctions on Russia and Iran, congressional aides said on Thursday, and one lawmaker said the matter could be resolved as soon as Friday.

"I think as soon as tomorrow, the House (of Representatives) could pass it out," Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee and an author of the bill, told reporters.

He said he expected the House to make changes that would not affect the bill's overall character and to address issues that have worried energy companies, such as a provision that oil firms said could block them out of international exploration projects if Russian firms were also involved.

Hoping to send a message to President Donald Trump to maintain a strong line against Moscow, the Senate passed the sanctions on Russia, part of a broader measure also imposing new sanctions on Iran, by 98-2 on June 15.

The bill has been mired in the House ever since.

The delay has frustrated Democrats, and some of Trump's fellow Republicans, who think the president is so eager to improve relations with Russia that he will not retaliate for Moscow's international aggression.

This week, Trump has been defending his oldest son, Donald Trump Jr., who met with a Russian lawyer during the 2016 campaign after he was told she might have damaging information about Democratic candidate Hillary Clinton.

Republicans, who control Congress, said the House could not vote on the Senate bill because it violated a constitutional requirement that legislation affecting government revenues originate in the House.

Democrats accused Republicans of stalling because of Trump administration concern about a provision setting up a process for Congress to approve any effort by the president to ease sanctions on Russia.

Seeking a greater influence in foreign policy, Congress has included such "review" provisions in a few recent major bills, starting with Corker's 2015 legislation forcing congressional review of President Barack Obama's nuclear deal with Iran.

Corker said he thought there should be more congressional review of foreign policy. "It's been my goal as chairman just to bring back our equivalent status to the executive branch, and this is one way of doing so."

House aides said negotiations on the Russia bill were continuing.

"No deal has been reached, but talks have been productive and will continue," said AshLee Strong, a spokeswoman for House Speaker Paul Ryan.