The Russian rouble weakened on Monday, sliding to its lowest point since early-May against the dollar, under pressure from low oil prices, reduced foreign currency supply and the prospect of more sanctions against Moscow.

At 0749 GMT, the rouble was 1.7% weaker against the dollar at 79.25, its weakest point since May 4.

It had lost 1.7% to trade at 86.25 versus the euro and had shed 2.3% against the yuan to 11.38.

Leaders of the Group of Seven (G7) nations plan to tighten sanctions on Russia at their summit in Japan this week, with steps aimed at energy and exports aiding Moscow’s military effort in Ukraine, officials with direct knowledge of the discussions said.

The people said new measures would target sanctions evasion involving third countries, and seek to undermine Russia’s future energy production and curb trade that supports Russia’s military.

“There is nothing particularly scary in the (sanctions the West is due to announce),” said Alor Broker in a note.

“But for now this factor psychologically weighs on rouble assets.” Brent crude oil, a global benchmark for Russia’s main export, was up 0.1% at $74.21 a barrel, near a 10-day low.

Russian rouble turns negative after hitting eight-week high

The lower supply of foreign currency may also hamper the rouble, said Banki.ru chief analyst Bogdan Zvarich, although that downward pressure should gradually ease as exporters prepare to pay taxes towards the end of the month. Russian stock indexes were mixed.

The dollar-denominated RTS index was down 0.7% to 1,030.7 points.

The rouble-based MOEX Russian index was 1.1% higher at 2,594.5 points.