House Republicans, warning that President Reagan is serious about vetoing spending bills that bust his budget, came within an eyelash yesterday of blocking an appropriation that is about $1 billion above what the president wants.

In one of this fall's first tests of strength in the House on spending, a GOP effort to recommit a conference report on the $7.5 billion Interior Department money bill failed on a tie, 199 to 199.

House and Senate conferees, meanwhile, also agreed on a $10.5 billion Transportation Department appropriation bill that is an estimated $850 million to $900 million over the president's request. Details, Page D8

The House vote foreshadowed close contests on spending bills in the closing weeks of Congress and also indicated that if Reagan goes to the mat with vetoes the House Republicans can probably sustain him.

That was the warning from several Republicans who complained yesterday that appropriation bills heading toward final passage in the next few weeks will push the federal deficits ever higher.

"If the president has an opportunity to register his will, he will veto this," warned Rep. Robert H. Michel (R-Ill.), the minority leader. He also predicted that Republicans can muster 140 or 150 votes to sustain a veto.

Twenty-nine Democrats voted with 170 Republicans for the recommittal motion. Eight Republicans joined with 191 Democrats in opposing it.

At a news conference Tuesday, the president reiterated a threat to veto what he calls "budget-busting" bills, none of which has reached his desk yet. While agreeing to postpone further cuts in entitlement programs and ideas for new tax increases, he has continued to insist on appropriations 12 percent below the levels he first proposed last March.

Several appropriation bills wending their way through conference committees or awaiting Senate action would exceed that level. The House in September approved a conference report on an appropriation for the Department of Housing and Urban Development that is more than $1 billion above what the president now wants.

The Interior bill, with money for forests, parks and Indian affairs, is now next in line. It provided the first test of House sentiment since Reagan's news conference on Tuesday, and Democrats were forced to go all out to beat back the recommittal motion. The bill then passed by voice vote; it is slightly more than $1 billion over the level of Reagan's September request for new cuts.

The House has now passed 11 appropriation bills and, with yesterday's action, has finished two conference reports resolving conflicts with the Senate.

The Senate, meanwhile, which is well behind this pace, waded into another bill that is nearly a half-billion dollars above the president's September ceiling, appropriating $8.6 billion for the Commerce, Justice and State departments and the judiciary. During an afternoon and evening of debate no strong GOP move to trim it was apparent.

Last night the Senate shifted to grain and trade embargos against the Soviet Union. It passed, 66 to 20, a bill introduced by Sen. Charles H. Percy (R-Ill.) to give Congress a voice in those embargos. It provides that a presidential embargo on agricultural commodities would expire after 60 days unless Congress has acted to endorse it.