BALTIMORE (Reuters) - A federal judge on Friday refused to dismiss antitrust charges filed against Microsoft in separate cases by Sun Microsystems Inc. SUNW.O and two small software companies.

Ruling simultaneously on suits by Be Inc. and Burst.com BRST.OB , U.S. District Judge J. Frederick Motz said he would allow the cases to proceed.

"I am satisfied there are sufficient allegations as to federal antitrust claims," Motz said in court after hearing arguments from the parties.

Motz also denied Microsoft's request that he throw out some of the charges brought by Sun in its antitrust suit against the world's largest software company.

Last month Motz sided with Sun, saying he would issue a preliminary injunction ordering Microsoft to distribute Sun's Java programming language in its Windows operating system.

Be, which dissolved as a company last year, has alleged it was excluded from competing in the market for computer operating systems when Microsoft pressured computer makers not to ship computers with two operating systems.

Be sold its operating system to handheld device maker Palm Inc. PALM.O in 2001.

Burst, based in Santa Rosa, California, said Microsoft forced it out of the market for video-streaming software by pressuring chip maker Intel Corp. INTC.O and RealNetworks Inc. RNWK.O not to support Burst technologies.

Attorneys for Microsoft said the Be and Burst cases should be thrown out, saying not all Microsoft's tactics were anti-competitive and questioning whether the two small companies were harmed.

Motz has been assigned cases arising from the landmark government antitrust suit filed in 1998, including a private suit by AOL Time Warner AOL.N and class actions suits on behalf of consumers.

Two states, Massachusetts and West Virginia, have appealed as too weak a settlement of the government case endorsed by U.S. District Judge Colleen Kollar Kotelly in November.

The U.S. Court of Appeals for the District of Columbia, in 2001, agreed that Microsoft had illegally maintained its monopoly in the Windows computer operating system but rejected breaking the company in two to prevent future violations.

Microsoft on Friday argued that Motz should dismiss some of Sun's charges that it was harmed by Microsoft illegally tying its Internet browser and other software to Windows.

But Motz was not swayed, saying: "Obviously there are serious issues related to the tying claim."

Both Microsoft and Sun told Motz they were having difficulty agreeing on the exact terms of the preliminary injunction requiring Microsoft to include Sun's Java software in Windows.

Sun attorney Rusty Day said that Microsoft had sent a lengthy counter proposal in the early hours of Friday.

"I didn't think it was going to be that major a deal," said Motz, adding he didn't want the case delayed and scheduled talks in his chambers on the wording.