Dutch PM Mark Rutte said he had told Russian President Vladimir Putin that time was "running out" to show he could help. Most crash victims were Dutch.
The US and Britain also told Russia full access to the area was needed.
International observers have had their movements restricted by pro-Russia militiamen who control the crash site.
The US said it was "deeply concerned" at the limited access at the crash site.
"It is critical that there be a full, credible, and unimpeded international investigation as quickly as possible," said a statement from the State Department in Washington.
Both Ukraine and the pro-Russian rebels have accused each other of shooting down the Boeing 777, which was flying from Amsterdam to Kuala Lumpur.
Flight MH17 was reportedly hit by a missile over a rebel-held area in Donetsk region on Thursday. All 298 people on board died.
