Freshman U.S. Sen. John W. Warner of Virginia asked his Maryland Republican colleague Sen. Charles McC. Mathias this week to tag along with him in sponsoring a bill that could resolve Metro's subway financing dilemma.

But instead of winning praise for a gesture of regional cooperation, Warner, who has held elective office less than three months, got a lesson in protocol from Mathias' staff.

It seems that Mathias, Maryland's senior senator, already has his own Metro financing bill and, if there were to be any cosponsoring, Warner would have to join Mathias -- not the other way around.

The confusion arose after Warner's office issued a press release inviting elected officials from Northern Virginia to a meeting next Tuesday "to discuss federal legislation Sen. Warner plans to introduce to provide capital, operating and bond-retirement funds for Metrorail."

In an interview in Warner's Senate suite, two Warner aides said they were aware that Rep. Herbert E. Harris II (D-Va.) already had introduced a Metro financing bill in the House. But they said the Warner bill would allow the Senate "to modify or withdraw" the Harris proposal if it didn't look as if it would pass.

"He (Warner) and Mac (Mathias) are working on this, and Mathias is a potential cosponsor," the Warner aide explained.

When Mathias' office was asked by a reporter about Warner's proposed cooperative venture, a long silence followed. "The red flags popped up all over the place," a Mathias aide said later.

"Give us a moment to call Warner's office for clarification," said the wary Mathias assistant, adding, "and then you should get back to Warner's people."

The call back to Warner's office produced a norvous laugh from a Warner staffer. The aide said the reporter must have misunderstood, and, of course, Mathias was the senior senator who has been working for years on solutions to Metro financing. He also said that Warner knew Mathias had his own bill.

The next day, Warner summoned the reporter to his office. Flanked by four aides taking notes, Warner began:

"We are working from Mac's legislation. That is the starting point. He is the senior person actively working on it. He has the corporate knowledge, and I'm delighted to cosponsor with him.

"There's not likely to be a separate Warner proposal," the shirt-sleeved Warner emphasized. "I don't know how that happened.'

Back at Mathias' office in the Russell Senate Office Building, three aides to the Maryland senator reported that Warner bad personally stopped by to explain the foul-up to them. Mathias was in West Germany, speaking to the Atlantic Conference in Hamburg, but Warner invited Mathias' staff to return with him to the Dirksen Building to meet with his staff.

"Warner screwed up and all we wanted him to do was admit it," a Mathias aide said.

"He made a mistake," added another Mathias assistant. And in a reference to Warner's much-criticized predecessor, the aide added sympathetically, "At least he's not another Bill Scott."