Defensive lineman Markus Koch, the Washington Redskins' top draft choice, today agreed to a three-year contract believed to be worth about $700,000, plus a signing bonus of about $200,000.

Koch, a Canadian citizen, said tonight over the phone he had to wait a week to get into the United States after he was denied entry because of visa problems.

He eventually obtained a work visa and entered the country last Saturday.

He also said authorities at the border near Buffalo searched his car before he was turned away July 13.

"I guess they thought I was carrying drugs or smuggling something in," Koch said. "I wasn't doing either. I guess they check scraggly looking guys like myself. I'm a dangerous-looking guy."

Koch, who is 6 feet 5, weighs 275 pounds and is growing a beard, said he expects to get to training camp by late Wednesday morning.

"I knew it wasn't great for me to not be in camp, but it was something that was inevitable with the situation of slow signings of draft choices this year," he said.

Veteran tight end Clint Didier, who has been bothered by injuries often in his five seasons, suffered a mild strain of his right hamstring while running a pass pattern this morning and worked out in shorts and a T-shirt this afternoon.

In 1981, Didier missed his entire rookie season because of a pulled hamstring. In 1984, he broke his right fibula in preseason and missed five games. In 1985, he played about half of the season with a bruised kneecap.

Didier just signed a two-year contract worth $580,000.

The Redskins' kicking and punting battles start Wednesday, said special teams coach Wayne Sevier. His assessment of the kicking game so far? "We're not in midseason form yet, that's for sure."

Rookie free agent Richie White, a running back and punter from Central Arkansas, was waived today. The Redskins training camp roster stands at 79, with the veterans reporting Saturday.